On Thu, May 31, 2018 at 02:50:41AM -0400, Mathieu Desnoyers wrote:

----- On May 30, 2018, at 2:04 AM, Joel Fernandes joelaf@google.com wrote:

...

From: "Joel Fernandes (Google)" joel@joelfernandes.org

In recent tests with IRQ on/off tracepoints, a large performance overhead ~10% is noticed when running hackbench. This is root caused to calls to rcu_irq_enter_irqson and rcu_irq_exit_irqson from the tracepoint code. Following a long discussion on the list [1] about this, we concluded that srcu is a better alternative for use during rcu idle. Although it does involve extra barriers, its lighter than the sched-rcu version which has to do additional RCU calls to notify RCU idle about entry into RCU sections.

In this patch, we change the underlying implementation of the trace_*_rcuidle API to use SRCU. This has shown to improve performance alot for the high frequency irq enable/disable tracepoints.

Test: Tested idle and preempt/irq tracepoints.

Here are some performance numbers:

With a run of the following 30 times on a single core x86 Qemu instance with 1GB memory: hackbench -g 4 -f 2 -l 3000

Completion times in seconds. CONFIG_PROVE_LOCKING=y.

No patches (without this series) Mean: 3.048 Median: 3.025 Std Dev: 0.064

With Lockdep using irq tracepoints with RCU implementation: Mean: 3.451 (-11.66 %) Median: 3.447 (-12.22%) Std Dev: 0.049

With Lockdep using irq tracepoints with SRCU implementation (this series): Mean: 3.020 (I would consider the improvement against the "without this series" case as just noise). Median: 3.013 Std Dev: 0.033

[1] https://patchwork.kernel.org/patch/10344297/

Signed-off-by: Joel Fernandes (Google) joel@joelfernandes.org

include/linux/tracepoint.h | 48 +++++++++++++++++++++++++++++++------- kernel/tracepoint.c | 15 +++++++++++- 2 files changed, 54 insertions(+), 9 deletions(-)

diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h index c94f466d57ef..880794207921 100644 --- a/include/linux/tracepoint.h +++ b/include/linux/tracepoint.h @@ -15,6 +15,7 @@ */

#include <linux/smp.h> +#include <linux/srcu.h> #include <linux/errno.h> #include <linux/types.h> #include <linux/cpumask.h> @@ -33,6 +34,8 @@ struct trace_eval_map {

#define TRACEPOINT_DEFAULT_PRIO 10

+extern struct srcu_struct tracepoint_srcu;

extern int tracepoint_probe_register(struct tracepoint *tp, void *probe, void *data); extern int @@ -75,10 +78,15 @@ int unregister_tracepoint_module_notifier(struct notifier_block *nb)

• probe unregistration and the end of module exit to make sure there is no
• caller executing a probe when it is freed.

*/ +#ifdef CONFIG_TRACEPOINTS static inline void tracepoint_synchronize_unregister(void) {

• synchronize_srcu(&tracepoint_srcu); synchronize_sched();

} +#else +static inline void tracepoint_synchronize_unregister(void) { }

In order to add some consistency to the style in this header file, this empty function should look like:

static inline void tracepoint_synchronize_unregister(void) { }

(with newline before "{")

Ok, I changed it to the style you're proposing.

...

+#endif

#ifdef CONFIG_HAVE_SYSCALL_TRACEPOINTS extern int syscall_regfunc(void); @@ -129,18 +137,38 @@ extern void syscall_unregfunc(void);

• as "(void *, void)". The DECLARE_TRACE_NOARGS() will pass in just
• "void *data", where as the DECLARE_TRACE() will pass in "void *data, proto".

*/ -#define __DO_TRACE(tp, proto, args, cond, rcucheck) \ +#define __DO_TRACE(tp, proto, args, cond, rcuidle) \ do { \ struct tracepoint_func *it_func_ptr; \ void *it_func; \ void *__data; \

• int __maybe_unused idx = 0;				\
  						\
  

  if (!(cond)) \ return; \

• if (rcucheck)						\
  

• 	rcu_irq_enter_irqson();				\
  

• rcu_read_lock_sched_notrace();				\
  

• it_func_ptr = rcu_dereference_sched((tp)->funcs);	\
  

• 							\
  

• /*							\
  

•  * For rcuidle callers, use srcu since sched-rcu	\
  

•  * doesn't work from the idle path.			\
  

•  */							\
  

• if (rcuidle) {						\
  

• 	if (in_nmi()) {					\
  

• 		WARN_ON_ONCE(1);			\
  

• 		return; /* no srcu from nmi */		\
  

I find it odd to have a "return" in a macro that consists of a do { } while (0). I'm tempted to replace "return" by "break" here, to break the macro do/while (0) loop.

"return;" is also used from "if (!(cond))" above so I prefer be consistent and just use return than break as done above, but please let me know if you still object.

...

• 	}						\
  

• 							\
  

• 	idx = srcu_read_lock_notrace(&tracepoint_srcu);	\
  

• 	it_func_ptr =					\
  

• 		srcu_dereference_notrace((tp)->funcs,	\
  

• 				&tracepoint_srcu);	\
  

• 	/* To keep it consistent with !rcuidle path */	\
  

• 	preempt_disable_notrace();			\
  

• } else {						\
  

• 	rcu_read_lock_sched_notrace();			\
  

• 	it_func_ptr =					\
  

• 		rcu_dereference_sched((tp)->funcs);	\
  

• }							\
  

• 							\
  

  if (it_func_ptr) { \ do { \ it_func = (it_func_ptr)->func; \

@@ -148,9 +176,13 @@ extern void syscall_unregfunc(void); ((void(*)(proto))(it_func))(args); \ } while ((++it_func_ptr)->func); \ } \

• rcu_read_unlock_sched_notrace();			\
  

• if (rcucheck)						\
  

• 	rcu_irq_exit_irqson();				\
  

• 							\
  

• if (rcuidle) {						\
  

• 	preempt_enable_notrace();			\
  

• 	srcu_read_unlock_notrace(&tracepoint_srcu, idx);\
  

• } else {						\
  

• 	rcu_read_unlock_sched_notrace();		\
  

• }							\
  

  } while (0)

#ifndef MODULE diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c index 1e37da2e0c25..54157792f5ab 100644 --- a/kernel/tracepoint.c +++ b/kernel/tracepoint.c @@ -31,6 +31,9 @@ extern struct tracepoint * const __start___tracepoints_ptrs[]; extern struct tracepoint * const __stop___tracepoints_ptrs[];

+DEFINE_SRCU(tracepoint_srcu); +EXPORT_SYMBOL_GPL(tracepoint_srcu);

/* Set to 1 to enable tracepoint debug output */ static const int tracepoint_debug;

@@ -67,16 +70,26 @@ static inline void *allocate_probes(int count) return p == NULL ? NULL : p->probes; }

-static void rcu_free_old_probes(struct rcu_head *head) +static void srcu_free_old_probes(struct rcu_head *head) { kfree(container_of(head, struct tp_probes, rcu)); }

+static void rcu_free_old_probes(struct rcu_head *head) +{

• call_srcu(&tracepoint_srcu, head, srcu_free_old_probes);

+}

static inline void release_probes(struct tracepoint_func *old) { if (old) { struct tp_probes *tp_probes = container_of(old, struct tp_probes, probes[0]);

• /*
  

•  * Tracepoint probes are protected by both sched RCU and SRCU,
  

•  * by calling the SRCU callback in the sched RCU callback we
  

•  * cover both cases. So lets chain the SRCU and RCU callbacks.
  

lets -> let's

But I would use a different wording for that sentence that does not include "let's" which is short for "let us", e.g.

"Chain the SRCU and sched RCU callbacks to wait for both grace periods."

Fixed, thanks.

With the comments above taken care of, please add my:

Reviewed-by: Mathieu Desnoyers mathieu.desnoyers@efficios.com

Will do, and thanks for the review!

Below is the updated patch.

- Joel

---8<-----------------------

From: "Joel Fernandes (Google)" joel@joelfernandes.org Date: Thu, 26 Apr 2018 20:44:07 -0700 Subject: [PATCH v8.1] tracepoint: Make rcuidle tracepoint callers use SRCU

In recent tests with IRQ on/off tracepoints, a large performance overhead ~10% is noticed when running hackbench. This is root caused to calls to rcu_irq_enter_irqson and rcu_irq_exit_irqson from the tracepoint code. Following a long discussion on the list [1] about this, we concluded that srcu is a better alternative for use during rcu idle. Although it does involve extra barriers, its lighter than the sched-rcu version which has to do additional RCU calls to notify RCU idle about entry into RCU sections.

In this patch, we change the underlying implementation of the trace_*_rcuidle API to use SRCU. This has shown to improve performance alot for the high frequency irq enable/disable tracepoints.

Test: Tested idle and preempt/irq tracepoints.

Here are some performance numbers:

With a run of the following 30 times on a single core x86 Qemu instance with 1GB memory: hackbench -g 4 -f 2 -l 3000

Completion times in seconds. CONFIG_PROVE_LOCKING=y.

No patches (without this series) Mean: 3.048 Median: 3.025 Std Dev: 0.064

With Lockdep using irq tracepoints with RCU implementation: Mean: 3.451 (-11.66 %) Median: 3.447 (-12.22%) Std Dev: 0.049

With Lockdep using irq tracepoints with SRCU implementation (this series): Mean: 3.020 (I would consider the improvement against the "without this series" case as just noise). Median: 3.013 Std Dev: 0.033

[1] https://patchwork.kernel.org/patch/10344297/

Reviewed-by: Mathieu Desnoyers mathieu.desnoyers@efficios.com Signed-off-by: Joel Fernandes (Google) joel@joelfernandes.org --- include/linux/tracepoint.h | 49 +++++++++++++++++++++++++++++++------- kernel/tracepoint.c | 16 ++++++++++++- 2 files changed, 56 insertions(+), 9 deletions(-)

diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h index c94f466d57ef..9cf2882d2ef4 100644 --- a/include/linux/tracepoint.h +++ b/include/linux/tracepoint.h @@ -15,6 +15,7 @@ */

#include <linux/smp.h> +#include <linux/srcu.h> #include <linux/errno.h> #include <linux/types.h> #include <linux/cpumask.h> @@ -33,6 +34,8 @@ struct trace_eval_map {

#define TRACEPOINT_DEFAULT_PRIO 10

+extern struct srcu_struct tracepoint_srcu; + extern int tracepoint_probe_register(struct tracepoint *tp, void *probe, void *data); extern int @@ -75,10 +78,16 @@ int unregister_tracepoint_module_notifier(struct notifier_block *nb) * probe unregistration and the end of module exit to make sure there is no * caller executing a probe when it is freed. */ +#ifdef CONFIG_TRACEPOINTS static inline void tracepoint_synchronize_unregister(void) { + synchronize_srcu(&tracepoint_srcu); synchronize_sched(); } +#else +static inline void tracepoint_synchronize_unregister(void) +{ } +#endif

#ifdef CONFIG_HAVE_SYSCALL_TRACEPOINTS extern int syscall_regfunc(void); @@ -129,18 +138,38 @@ extern void syscall_unregfunc(void); * as "(void *, void)". The DECLARE_TRACE_NOARGS() will pass in just * "void *data", where as the DECLARE_TRACE() will pass in "void *data, proto". */ -#define __DO_TRACE(tp, proto, args, cond, rcucheck) \ +#define __DO_TRACE(tp, proto, args, cond, rcuidle) \ do { \ struct tracepoint_func *it_func_ptr; \ void *it_func; \ void *__data; \ + int __maybe_unused idx = 0; \ \ if (!(cond)) \ return; \ - if (rcucheck) \ - rcu_irq_enter_irqson(); \ - rcu_read_lock_sched_notrace(); \ - it_func_ptr = rcu_dereference_sched((tp)->funcs); \ + \ + /* \ + * For rcuidle callers, use srcu since sched-rcu \ + * doesn't work from the idle path. \ + */ \ + if (rcuidle) { \ + if (in_nmi()) { \ + WARN_ON_ONCE(1); \ + return; /* no srcu from nmi */ \ + } \ + \ + idx = srcu_read_lock_notrace(&tracepoint_srcu); \ + it_func_ptr = \ + srcu_dereference_notrace((tp)->funcs, \ + &tracepoint_srcu); \ + /* To keep it consistent with !rcuidle path */ \ + preempt_disable_notrace(); \ + } else { \ + rcu_read_lock_sched_notrace(); \ + it_func_ptr = \ + rcu_dereference_sched((tp)->funcs); \ + } \ + \ if (it_func_ptr) { \ do { \ it_func = (it_func_ptr)->func; \ @@ -148,9 +177,13 @@ extern void syscall_unregfunc(void); ((void(*)(proto))(it_func))(args); \ } while ((++it_func_ptr)->func); \ } \ - rcu_read_unlock_sched_notrace(); \ - if (rcucheck) \ - rcu_irq_exit_irqson(); \ + \ + if (rcuidle) { \ + preempt_enable_notrace(); \ + srcu_read_unlock_notrace(&tracepoint_srcu, idx);\ + } else { \ + rcu_read_unlock_sched_notrace(); \ + } \ } while (0)

#ifndef MODULE diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c index 1e37da2e0c25..b2e3be589aff 100644 --- a/kernel/tracepoint.c +++ b/kernel/tracepoint.c @@ -31,6 +31,9 @@ extern struct tracepoint * const __start___tracepoints_ptrs[]; extern struct tracepoint * const __stop___tracepoints_ptrs[];

+DEFINE_SRCU(tracepoint_srcu); +EXPORT_SYMBOL_GPL(tracepoint_srcu); + /* Set to 1 to enable tracepoint debug output */ static const int tracepoint_debug;

@@ -67,16 +70,27 @@ static inline void *allocate_probes(int count) return p == NULL ? NULL : p->probes; }

-static void rcu_free_old_probes(struct rcu_head *head) +static void srcu_free_old_probes(struct rcu_head *head) { kfree(container_of(head, struct tp_probes, rcu)); }

+static void rcu_free_old_probes(struct rcu_head *head) +{ + call_srcu(&tracepoint_srcu, head, srcu_free_old_probes); +} + static inline void release_probes(struct tracepoint_func *old) { if (old) { struct tp_probes *tp_probes = container_of(old, struct tp_probes, probes[0]); + /* + * Tracepoint probes are protected by both sched RCU and SRCU, + * by calling the SRCU callback in the sched RCU callback we + * cover both cases. So let us chain the SRCU and sched RCU + * callbacks to wait for both grace periods. + */ call_rcu_sched(&tp_probes->rcu, rcu_free_old_probes); } }

On Thu, May 31, 2018 at 10:56:39AM +0900, Namhyung Kim wrote:

On Tue, May 29, 2018 at 05:04:58PM -0700, Joel Fernandes wrote:

...

From: "Joel Fernandes (Google)" joel@joelfernandes.org

This patch detaches the preemptirq tracepoints from the tracers and keeps it separate.

Advantages:

• Lockdep and irqsoff event can now run in parallel since they no longer

have their own calls.

• This unifies the usecase of adding hooks to an irqsoff and irqson

event, and a preemptoff and preempton event. 3 users of the events exist:

• Lockdep
• irqsoff and preemptoff tracers
• irqs and preempt trace events

The unification cleans up several ifdefs and makes the code in preempt tracer and irqsoff tracers simpler. It gets rid of all the horrific ifdeferry around PROVE_LOCKING and makes configuration of the different users of the tracepoints more easy and understandable. It also gets rid of the time_* function calls from the lockdep hooks used to call into the preemptirq tracer which is not needed anymore. The negative delta in lines of code in this patch is quite large too.

In the patch we introduce a new CONFIG option PREEMPTIRQ_TRACEPOINTS as a single point for registering probes onto the tracepoints. With this, the web of config options for preempt/irq toggle tracepoints and its users becomes:

PREEMPT_TRACER PREEMPTIRQ_EVENTS IRQSOFF_TRACER PROVE_LOCKING | | \ | | \ (selects) / \ \ (selects) / TRACE_PREEMPT_TOGGLE ----> TRACE_IRQFLAGS \ / \ (depends on) / PREEMPTIRQ_TRACEPOINTS

One note, I have to check for lockdep recursion in the code that calls the trace events API and bail out if we're in lockdep recursion protection to prevent something like the following case: a spin_lock is taken. Then lockdep_acquired is called. That does a raw_local_irq_save and then sets lockdep_recursion, and then calls __lockdep_acquired. In this function, a call to get_lock_stats happens which calls preempt_disable, which calls trace IRQS off somewhere which enters my tracepoint code and sets the tracing_irq_cpu flag to prevent recursion. This flag is then never cleared causing lockdep paths to never be entered and thus causing splats and other bad things.

Other than the performance tests mentioned in the previous patch, I also ran the locking API test suite. I verified that all tests cases are passing.

I also injected issues by not registering lockdep probes onto the tracepoints and I see failures to confirm that the probes are indeed working.

Without probes:

[ 0.000000] hard-irqs-on + irq-safe-A/21: ok | ok | ok | [ 0.000000] soft-irqs-on + irq-safe-A/21: ok | ok | ok | [ 0.000000] sirq-safe-A => hirqs-on/12: ok | ok | ok | [ 0.000000] sirq-safe-A => hirqs-on/21: ok | ok | ok | [ 0.000000] hard-safe-A + irqs-on/12: ok | ok | ok | [ 0.000000] soft-safe-A + irqs-on/12: ok | ok | ok | [ 0.000000] hard-safe-A + irqs-on/21: ok | ok | ok | [ 0.000000] soft-safe-A + irqs-on/21: ok | ok | ok | [ 0.000000] hard-safe-A + unsafe-B #1/123: ok | ok | ok | [ 0.000000] soft-safe-A + unsafe-B #1/123: ok | ok | ok |

With probes:

[ 0.000000] hard-irqs-on + irq-safe-A/21: ok | ok | ok | [ 0.000000] soft-irqs-on + irq-safe-A/21: ok | ok | ok | [ 0.000000] sirq-safe-A => hirqs-on/12:FAILED|FAILED| ok | [ 0.000000] sirq-safe-A => hirqs-on/21:FAILED|FAILED| ok | [ 0.000000] hard-safe-A + irqs-on/12:FAILED|FAILED| ok | [ 0.000000] soft-safe-A + irqs-on/12:FAILED|FAILED| ok | [ 0.000000] hard-safe-A + irqs-on/21:FAILED|FAILED| ok | [ 0.000000] soft-safe-A + irqs-on/21:FAILED|FAILED| ok | [ 0.000000] hard-safe-A + unsafe-B #1/123: ok | ok | ok | [ 0.000000] soft-safe-A + unsafe-B #1/123: ok | ok | ok |

Signed-off-by: Joel Fernandes (Google) joel@joelfernandes.org

Reviewed-by: Namhyung Kim namhyung@kernel.org

Thanks a lot Namhyung for the review, Also I swapped the 'With probes' and 'Without probes' in the commit message above. Below is the updated patch with commit message fixed up and your Reviewed-by.

Steve, Ingo, does this patch series look Ok to you?

---8<-----------------------

From: "Joel Fernandes (Google)" joel@joelfernandes.org Date: Mon, 16 Apr 2018 20:18:00 -0700 Subject: [PATCH v8.1 6/8] tracing: Centralize preemptirq tracepoints and unify their usage

This patch detaches the preemptirq tracepoints from the tracers and keeps it separate.

Advantages: * Lockdep and irqsoff event can now run in parallel since they no longer have their own calls.

* This unifies the usecase of adding hooks to an irqsoff and irqson event, and a preemptoff and preempton event. 3 users of the events exist: - Lockdep - irqsoff and preemptoff tracers - irqs and preempt trace events

The unification cleans up several ifdefs and makes the code in preempt tracer and irqsoff tracers simpler. It gets rid of all the horrific ifdeferry around PROVE_LOCKING and makes configuration of the different users of the tracepoints more easy and understandable. It also gets rid of the time_* function calls from the lockdep hooks used to call into the preemptirq tracer which is not needed anymore. The negative delta in lines of code in this patch is quite large too.

In the patch we introduce a new CONFIG option PREEMPTIRQ_TRACEPOINTS as a single point for registering probes onto the tracepoints. With this, the web of config options for preempt/irq toggle tracepoints and its users becomes:

PREEMPT_TRACER PREEMPTIRQ_EVENTS IRQSOFF_TRACER PROVE_LOCKING | | \ | | \ (selects) / \ \ (selects) / TRACE_PREEMPT_TOGGLE ----> TRACE_IRQFLAGS \ / \ (depends on) / PREEMPTIRQ_TRACEPOINTS

One note, I have to check for lockdep recursion in the code that calls the trace events API and bail out if we're in lockdep recursion protection to prevent something like the following case: a spin_lock is taken. Then lockdep_acquired is called. That does a raw_local_irq_save and then sets lockdep_recursion, and then calls __lockdep_acquired. In this function, a call to get_lock_stats happens which calls preempt_disable, which calls trace IRQS off somewhere which enters my tracepoint code and sets the tracing_irq_cpu flag to prevent recursion. This flag is then never cleared causing lockdep paths to never be entered and thus causing splats and other bad things.

Other than the performance tests mentioned in the previous patch, I also ran the locking API test suite. I verified that all tests cases are passing.

I also injected issues by not registering lockdep probes onto the tracepoints and I see failures to confirm that the probes are indeed working.

This series + lockdep probes not registered (just to inject errors): [ 0.000000] hard-irqs-on + irq-safe-A/21: ok | ok | ok | [ 0.000000] soft-irqs-on + irq-safe-A/21: ok | ok | ok | [ 0.000000] sirq-safe-A => hirqs-on/12:FAILED|FAILED| ok | [ 0.000000] sirq-safe-A => hirqs-on/21:FAILED|FAILED| ok | [ 0.000000] hard-safe-A + irqs-on/12:FAILED|FAILED| ok | [ 0.000000] soft-safe-A + irqs-on/12:FAILED|FAILED| ok | [ 0.000000] hard-safe-A + irqs-on/21:FAILED|FAILED| ok | [ 0.000000] soft-safe-A + irqs-on/21:FAILED|FAILED| ok | [ 0.000000] hard-safe-A + unsafe-B #1/123: ok | ok | ok | [ 0.000000] soft-safe-A + unsafe-B #1/123: ok | ok | ok |

With this series + lockdep probes registered, all locking tests pass:

[ 0.000000] hard-irqs-on + irq-safe-A/21: ok | ok | ok | [ 0.000000] soft-irqs-on + irq-safe-A/21: ok | ok | ok | [ 0.000000] sirq-safe-A => hirqs-on/12: ok | ok | ok | [ 0.000000] sirq-safe-A => hirqs-on/21: ok | ok | ok | [ 0.000000] hard-safe-A + irqs-on/12: ok | ok | ok | [ 0.000000] soft-safe-A + irqs-on/12: ok | ok | ok | [ 0.000000] hard-safe-A + irqs-on/21: ok | ok | ok | [ 0.000000] soft-safe-A + irqs-on/21: ok | ok | ok | [ 0.000000] hard-safe-A + unsafe-B #1/123: ok | ok | ok | [ 0.000000] soft-safe-A + unsafe-B #1/123: ok | ok | ok |

Reviewed-by: Namhyung Kim namhyung@kernel.org Signed-off-by: Joel Fernandes (Google) joel@joelfernandes.org --- include/linux/ftrace.h | 11 +- include/linux/irqflags.h | 11 +- include/linux/lockdep.h | 8 +- include/linux/preempt.h | 2 +- include/trace/events/preemptirq.h | 23 +-- init/main.c | 5 +- kernel/locking/lockdep.c | 35 ++--- kernel/sched/core.c | 2 +- kernel/trace/Kconfig | 22 ++- kernel/trace/Makefile | 2 +- kernel/trace/trace_irqsoff.c | 231 ++++++++---------------------- kernel/trace/trace_preemptirq.c | 71 +++++++++ 12 files changed, 194 insertions(+), 229 deletions(-) create mode 100644 kernel/trace/trace_preemptirq.c

diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h index 9c3c9a319e48..5191030af0c0 100644 --- a/include/linux/ftrace.h +++ b/include/linux/ftrace.h @@ -709,16 +709,7 @@ static inline unsigned long get_lock_parent_ip(void) return CALLER_ADDR2; }

-#ifdef CONFIG_IRQSOFF_TRACER - extern void time_hardirqs_on(unsigned long a0, unsigned long a1); - extern void time_hardirqs_off(unsigned long a0, unsigned long a1); -#else - static inline void time_hardirqs_on(unsigned long a0, unsigned long a1) { } - static inline void time_hardirqs_off(unsigned long a0, unsigned long a1) { } -#endif - -#if defined(CONFIG_PREEMPT_TRACER) || \ - (defined(CONFIG_DEBUG_PREEMPT) && defined(CONFIG_PREEMPTIRQ_EVENTS)) +#ifdef CONFIG_TRACE_PREEMPT_TOGGLE extern void trace_preempt_on(unsigned long a0, unsigned long a1); extern void trace_preempt_off(unsigned long a0, unsigned long a1); #else diff --git a/include/linux/irqflags.h b/include/linux/irqflags.h index 9700f00bbc04..50edb9cbbd26 100644 --- a/include/linux/irqflags.h +++ b/include/linux/irqflags.h @@ -15,9 +15,16 @@ #include <linux/typecheck.h> #include <asm/irqflags.h>

-#ifdef CONFIG_TRACE_IRQFLAGS +/* Currently trace_softirqs_on/off is used only by lockdep */ +#ifdef CONFIG_PROVE_LOCKING extern void trace_softirqs_on(unsigned long ip); extern void trace_softirqs_off(unsigned long ip); +#else +# define trace_softirqs_on(ip) do { } while (0) +# define trace_softirqs_off(ip) do { } while (0) +#endif + +#ifdef CONFIG_TRACE_IRQFLAGS extern void trace_hardirqs_on(void); extern void trace_hardirqs_off(void); # define trace_hardirq_context(p) ((p)->hardirq_context) @@ -43,8 +50,6 @@ do { \ #else # define trace_hardirqs_on() do { } while (0) # define trace_hardirqs_off() do { } while (0) -# define trace_softirqs_on(ip) do { } while (0) -# define trace_softirqs_off(ip) do { } while (0) # define trace_hardirq_context(p) 0 # define trace_softirq_context(p) 0 # define trace_hardirqs_enabled(p) 0 diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h index 6fc77d4dbdcd..a8113357ceeb 100644 --- a/include/linux/lockdep.h +++ b/include/linux/lockdep.h @@ -266,7 +266,8 @@ struct held_lock { /* * Initialization, self-test and debugging-output methods: */ -extern void lockdep_info(void); +extern void lockdep_init(void); +extern void lockdep_init_early(void); extern void lockdep_reset(void); extern void lockdep_reset_lock(struct lockdep_map *lock); extern void lockdep_free_key_range(void *start, unsigned long size); @@ -406,7 +407,8 @@ static inline void lockdep_on(void) # define lock_downgrade(l, i) do { } while (0) # define lock_set_class(l, n, k, s, i) do { } while (0) # define lock_set_subclass(l, s, i) do { } while (0) -# define lockdep_info() do { } while (0) +# define lockdep_init() do { } while (0) +# define lockdep_init_early() do { } while (0) # define lockdep_init_map(lock, name, key, sub) \ do { (void)(name); (void)(key); } while (0) # define lockdep_set_class(lock, key) do { (void)(key); } while (0) @@ -532,7 +534,7 @@ do { \

#endif /* CONFIG_LOCKDEP */

-#ifdef CONFIG_TRACE_IRQFLAGS +#ifdef CONFIG_PROVE_LOCKING extern void print_irqtrace_events(struct task_struct *curr); #else static inline void print_irqtrace_events(struct task_struct *curr) diff --git a/include/linux/preempt.h b/include/linux/preempt.h index 5bd3f151da78..c01813c3fbe9 100644 --- a/include/linux/preempt.h +++ b/include/linux/preempt.h @@ -150,7 +150,7 @@ */ #define in_atomic_preempt_off() (preempt_count() != PREEMPT_DISABLE_OFFSET)

-#if defined(CONFIG_DEBUG_PREEMPT) || defined(CONFIG_PREEMPT_TRACER) +#if defined(CONFIG_DEBUG_PREEMPT) || defined(CONFIG_TRACE_PREEMPT_TOGGLE) extern void preempt_count_add(int val); extern void preempt_count_sub(int val); #define preempt_count_dec_and_test() \ diff --git a/include/trace/events/preemptirq.h b/include/trace/events/preemptirq.h index 9c4eb33c5a1d..9a0d4ceeb166 100644 --- a/include/trace/events/preemptirq.h +++ b/include/trace/events/preemptirq.h @@ -1,4 +1,4 @@ -#ifdef CONFIG_PREEMPTIRQ_EVENTS +#ifdef CONFIG_PREEMPTIRQ_TRACEPOINTS

#undef TRACE_SYSTEM #define TRACE_SYSTEM preemptirq @@ -32,7 +32,7 @@ DECLARE_EVENT_CLASS(preemptirq_template, (void *)((unsigned long)(_stext) + __entry->parent_offs)) );

-#ifndef CONFIG_PROVE_LOCKING +#ifdef CONFIG_TRACE_IRQFLAGS DEFINE_EVENT(preemptirq_template, irq_disable, TP_PROTO(unsigned long ip, unsigned long parent_ip), TP_ARGS(ip, parent_ip)); @@ -40,9 +40,14 @@ DEFINE_EVENT(preemptirq_template, irq_disable, DEFINE_EVENT(preemptirq_template, irq_enable, TP_PROTO(unsigned long ip, unsigned long parent_ip), TP_ARGS(ip, parent_ip)); +#else +#define trace_irq_enable(...) +#define trace_irq_disable(...) +#define trace_irq_enable_rcuidle(...) +#define trace_irq_disable_rcuidle(...) #endif

-#ifdef CONFIG_DEBUG_PREEMPT +#ifdef CONFIG_TRACE_PREEMPT_TOGGLE DEFINE_EVENT(preemptirq_template, preempt_disable, TP_PROTO(unsigned long ip, unsigned long parent_ip), TP_ARGS(ip, parent_ip)); @@ -50,22 +55,22 @@ DEFINE_EVENT(preemptirq_template, preempt_disable, DEFINE_EVENT(preemptirq_template, preempt_enable, TP_PROTO(unsigned long ip, unsigned long parent_ip), TP_ARGS(ip, parent_ip)); +#else +#define trace_preempt_enable(...) +#define trace_preempt_disable(...) +#define trace_preempt_enable_rcuidle(...) +#define trace_preempt_disable_rcuidle(...) #endif

#endif /* _TRACE_PREEMPTIRQ_H */

#include <trace/define_trace.h>

-#endif /* !CONFIG_PREEMPTIRQ_EVENTS */ - -#if !defined(CONFIG_PREEMPTIRQ_EVENTS) || defined(CONFIG_PROVE_LOCKING) +#else /* !CONFIG_PREEMPTIRQ_TRACEPOINTS */ #define trace_irq_enable(...) #define trace_irq_disable(...) #define trace_irq_enable_rcuidle(...) #define trace_irq_disable_rcuidle(...) -#endif - -#if !defined(CONFIG_PREEMPTIRQ_EVENTS) || !defined(CONFIG_DEBUG_PREEMPT) #define trace_preempt_enable(...) #define trace_preempt_disable(...) #define trace_preempt_enable_rcuidle(...) diff --git a/init/main.c b/init/main.c index 3b4ada11ed52..44fe43be84c1 100644 --- a/init/main.c +++ b/init/main.c @@ -648,6 +648,9 @@ asmlinkage __visible void __init start_kernel(void) profile_init(); call_function_init(); WARN(!irqs_disabled(), "Interrupts were enabled early\n"); + + lockdep_init_early(); + early_boot_irqs_disabled = false; local_irq_enable();

@@ -663,7 +666,7 @@ asmlinkage __visible void __init start_kernel(void) panic("Too many boot %s vars at `%s'", panic_later, panic_param);

- lockdep_info(); + lockdep_init();

/* * Need to run this when irqs are enabled, because it wants diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c index 023386338269..871a42232858 100644 --- a/kernel/locking/lockdep.c +++ b/kernel/locking/lockdep.c @@ -55,6 +55,7 @@

#include "lockdep_internals.h"

+#include <trace/events/preemptirq.h> #define CREATE_TRACE_POINTS #include <trace/events/lock.h>

@@ -2841,10 +2842,9 @@ static void __trace_hardirqs_on_caller(unsigned long ip) debug_atomic_inc(hardirqs_on_events); }

-__visible void trace_hardirqs_on_caller(unsigned long ip) +static void lockdep_hardirqs_on(void *none, unsigned long ignore, + unsigned long ip) { - time_hardirqs_on(CALLER_ADDR0, ip); - if (unlikely(!debug_locks || current->lockdep_recursion)) return;

@@ -2883,23 +2883,15 @@ __visible void trace_hardirqs_on_caller(unsigned long ip) __trace_hardirqs_on_caller(ip); current->lockdep_recursion = 0; } -EXPORT_SYMBOL(trace_hardirqs_on_caller); - -void trace_hardirqs_on(void) -{ - trace_hardirqs_on_caller(CALLER_ADDR0); -} -EXPORT_SYMBOL(trace_hardirqs_on);

/* * Hardirqs were disabled: */ -__visible void trace_hardirqs_off_caller(unsigned long ip) +static void lockdep_hardirqs_off(void *none, unsigned long ignore, + unsigned long ip) { struct task_struct *curr = current;

- time_hardirqs_off(CALLER_ADDR0, ip); - if (unlikely(!debug_locks || current->lockdep_recursion)) return;

@@ -2921,13 +2913,6 @@ __visible void trace_hardirqs_off_caller(unsigned long ip) } else debug_atomic_inc(redundant_hardirqs_off); } -EXPORT_SYMBOL(trace_hardirqs_off_caller); - -void trace_hardirqs_off(void) -{ - trace_hardirqs_off_caller(CALLER_ADDR0); -} -EXPORT_SYMBOL(trace_hardirqs_off);

/* * Softirqs will be enabled: @@ -4334,7 +4319,15 @@ void lockdep_reset_lock(struct lockdep_map *lock) raw_local_irq_restore(flags); }

-void __init lockdep_info(void) +void __init lockdep_init_early(void) +{ +#ifdef CONFIG_PROVE_LOCKING + register_trace_prio_irq_disable(lockdep_hardirqs_off, NULL, INT_MAX); + register_trace_prio_irq_enable(lockdep_hardirqs_on, NULL, INT_MIN); +#endif +} + +void __init lockdep_init(void) { printk("Lock dependency validator: Copyright (c) 2006 Red Hat, Inc., Ingo Molnar\n");

diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 092f7c4de903..4e9c2d254fba 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -3189,7 +3189,7 @@ static inline void sched_tick_stop(int cpu) { } #endif

#if defined(CONFIG_PREEMPT) && (defined(CONFIG_DEBUG_PREEMPT) || \ - defined(CONFIG_PREEMPT_TRACER)) + defined(CONFIG_TRACE_PREEMPT_TOGGLE)) /* * If the value passed in is equal to the current preempt count * then we just disabled preemption. Start timing the latency. diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig index c4f0f2e4126e..0bcba2a76ad9 100644 --- a/kernel/trace/Kconfig +++ b/kernel/trace/Kconfig @@ -82,6 +82,15 @@ config RING_BUFFER_ALLOW_SWAP Allow the use of ring_buffer_swap_cpu. Adds a very slight overhead to tracing when enabled.

+config PREEMPTIRQ_TRACEPOINTS + bool + depends on TRACE_PREEMPT_TOGGLE || TRACE_IRQFLAGS + select TRACING + default y + help + Create preempt/irq toggle tracepoints if needed, so that other parts + of the kernel can use them to generate or add hooks to them. + # All tracer options should select GENERIC_TRACER. For those options that are # enabled by all tracers (context switch and event tracer) they select TRACING. # This allows those options to appear when no other tracer is selected. But the @@ -159,18 +168,20 @@ config FUNCTION_GRAPH_TRACER the return value. This is done by setting the current return address on the current task structure into a stack of calls.

+config TRACE_PREEMPT_TOGGLE + bool + help + Enables hooks which will be called when preemption is first disabled, + and last enabled.

config PREEMPTIRQ_EVENTS bool "Enable trace events for preempt and irq disable/enable" select TRACE_IRQFLAGS - depends on DEBUG_PREEMPT || !PROVE_LOCKING - depends on TRACING + select TRACE_PREEMPT_TOGGLE if PREEMPT + select GENERIC_TRACER default n help Enable tracing of disable and enable events for preemption and irqs. - For tracing preempt disable/enable events, DEBUG_PREEMPT must be - enabled. For tracing irq disable/enable events, PROVE_LOCKING must - be disabled.

config IRQSOFF_TRACER bool "Interrupts-off Latency Tracer" @@ -207,6 +218,7 @@ config PREEMPT_TRACER select RING_BUFFER_ALLOW_SWAP select TRACER_SNAPSHOT select TRACER_SNAPSHOT_PER_CPU_SWAP + select TRACE_PREEMPT_TOGGLE help This option measures the time spent in preemption-off critical sections, with microsecond accuracy. diff --git a/kernel/trace/Makefile b/kernel/trace/Makefile index e2538c7638d4..84a0cb222f20 100644 --- a/kernel/trace/Makefile +++ b/kernel/trace/Makefile @@ -35,7 +35,7 @@ obj-$(CONFIG_TRACING) += trace_printk.o obj-$(CONFIG_TRACING_MAP) += tracing_map.o obj-$(CONFIG_CONTEXT_SWITCH_TRACER) += trace_sched_switch.o obj-$(CONFIG_FUNCTION_TRACER) += trace_functions.o -obj-$(CONFIG_PREEMPTIRQ_EVENTS) += trace_irqsoff.o +obj-$(CONFIG_PREEMPTIRQ_TRACEPOINTS) += trace_preemptirq.o obj-$(CONFIG_IRQSOFF_TRACER) += trace_irqsoff.o obj-$(CONFIG_PREEMPT_TRACER) += trace_irqsoff.o obj-$(CONFIG_SCHED_TRACER) += trace_sched_wakeup.o diff --git a/kernel/trace/trace_irqsoff.c b/kernel/trace/trace_irqsoff.c index f8daa754cce2..770cd30cda40 100644 --- a/kernel/trace/trace_irqsoff.c +++ b/kernel/trace/trace_irqsoff.c @@ -16,7 +16,6 @@

#include "trace.h"

-#define CREATE_TRACE_POINTS #include <trace/events/preemptirq.h>

#if defined(CONFIG_IRQSOFF_TRACER) || defined(CONFIG_PREEMPT_TRACER) @@ -450,66 +449,6 @@ void stop_critical_timings(void) } EXPORT_SYMBOL_GPL(stop_critical_timings);

-#ifdef CONFIG_IRQSOFF_TRACER -#ifdef CONFIG_PROVE_LOCKING -void time_hardirqs_on(unsigned long a0, unsigned long a1) -{ - if (!preempt_trace() && irq_trace()) - stop_critical_timing(a0, a1); -} - -void time_hardirqs_off(unsigned long a0, unsigned long a1) -{ - if (!preempt_trace() && irq_trace()) - start_critical_timing(a0, a1); -} - -#else /* !CONFIG_PROVE_LOCKING */ - -/* - * We are only interested in hardirq on/off events: - */ -static inline void tracer_hardirqs_on(void) -{ - if (!preempt_trace() && irq_trace()) - stop_critical_timing(CALLER_ADDR0, CALLER_ADDR1); -} - -static inline void tracer_hardirqs_off(void) -{ - if (!preempt_trace() && irq_trace()) - start_critical_timing(CALLER_ADDR0, CALLER_ADDR1); -} - -static inline void tracer_hardirqs_on_caller(unsigned long caller_addr) -{ - if (!preempt_trace() && irq_trace()) - stop_critical_timing(CALLER_ADDR0, caller_addr); -} - -static inline void tracer_hardirqs_off_caller(unsigned long caller_addr) -{ - if (!preempt_trace() && irq_trace()) - start_critical_timing(CALLER_ADDR0, caller_addr); -} - -#endif /* CONFIG_PROVE_LOCKING */ -#endif /* CONFIG_IRQSOFF_TRACER */ - -#ifdef CONFIG_PREEMPT_TRACER -static inline void tracer_preempt_on(unsigned long a0, unsigned long a1) -{ - if (preempt_trace() && !irq_trace()) - stop_critical_timing(a0, a1); -} - -static inline void tracer_preempt_off(unsigned long a0, unsigned long a1) -{ - if (preempt_trace() && !irq_trace()) - start_critical_timing(a0, a1); -} -#endif /* CONFIG_PREEMPT_TRACER */ - #ifdef CONFIG_FUNCTION_TRACER static bool function_enabled;

@@ -659,15 +598,34 @@ static void irqsoff_tracer_stop(struct trace_array *tr) }

#ifdef CONFIG_IRQSOFF_TRACER +/* + * We are only interested in hardirq on/off events: + */ +static void tracer_hardirqs_on(void *none, unsigned long a0, unsigned long a1) +{ + if (!preempt_trace() && irq_trace()) + stop_critical_timing(a0, a1); +} + +static void tracer_hardirqs_off(void *none, unsigned long a0, unsigned long a1) +{ + if (!preempt_trace() && irq_trace()) + start_critical_timing(a0, a1); +} + static int irqsoff_tracer_init(struct trace_array *tr) { trace_type = TRACER_IRQS_OFF;

+ register_trace_irq_disable(tracer_hardirqs_off, NULL); + register_trace_irq_enable(tracer_hardirqs_on, NULL); return __irqsoff_tracer_init(tr); }

static void irqsoff_tracer_reset(struct trace_array *tr) { + unregister_trace_irq_disable(tracer_hardirqs_off, NULL); + unregister_trace_irq_enable(tracer_hardirqs_on, NULL); __irqsoff_tracer_reset(tr); }

@@ -690,21 +648,34 @@ static struct tracer irqsoff_tracer __read_mostly = .allow_instances = true, .use_max_tr = true, }; -# define register_irqsoff(trace) register_tracer(&trace) -#else -# define register_irqsoff(trace) do { } while (0) -#endif +#endif /* CONFIG_IRQSOFF_TRACER */

#ifdef CONFIG_PREEMPT_TRACER +static void tracer_preempt_on(void *none, unsigned long a0, unsigned long a1) +{ + if (preempt_trace() && !irq_trace()) + stop_critical_timing(a0, a1); +} + +static void tracer_preempt_off(void *none, unsigned long a0, unsigned long a1) +{ + if (preempt_trace() && !irq_trace()) + start_critical_timing(a0, a1); +} + static int preemptoff_tracer_init(struct trace_array *tr) { trace_type = TRACER_PREEMPT_OFF;

+ register_trace_preempt_disable(tracer_preempt_off, NULL); + register_trace_preempt_enable(tracer_preempt_on, NULL); return __irqsoff_tracer_init(tr); }

static void preemptoff_tracer_reset(struct trace_array *tr) { + unregister_trace_preempt_disable(tracer_preempt_off, NULL); + unregister_trace_preempt_enable(tracer_preempt_on, NULL); __irqsoff_tracer_reset(tr); }

@@ -727,23 +698,29 @@ static struct tracer preemptoff_tracer __read_mostly = .allow_instances = true, .use_max_tr = true, }; -# define register_preemptoff(trace) register_tracer(&trace) -#else -# define register_preemptoff(trace) do { } while (0) -#endif +#endif /* CONFIG_PREEMPT_TRACER */

-#if defined(CONFIG_IRQSOFF_TRACER) && \ - defined(CONFIG_PREEMPT_TRACER) +#if defined(CONFIG_IRQSOFF_TRACER) && defined(CONFIG_PREEMPT_TRACER)

static int preemptirqsoff_tracer_init(struct trace_array *tr) { trace_type = TRACER_IRQS_OFF | TRACER_PREEMPT_OFF;

+ register_trace_irq_disable(tracer_hardirqs_off, NULL); + register_trace_irq_enable(tracer_hardirqs_on, NULL); + register_trace_preempt_disable(tracer_preempt_off, NULL); + register_trace_preempt_enable(tracer_preempt_on, NULL); + return __irqsoff_tracer_init(tr); }

static void preemptirqsoff_tracer_reset(struct trace_array *tr) { + unregister_trace_irq_disable(tracer_hardirqs_off, NULL); + unregister_trace_irq_enable(tracer_hardirqs_on, NULL); + unregister_trace_preempt_disable(tracer_preempt_off, NULL); + unregister_trace_preempt_enable(tracer_preempt_on, NULL); + __irqsoff_tracer_reset(tr); }

@@ -766,115 +743,21 @@ static struct tracer preemptirqsoff_tracer __read_mostly = .allow_instances = true, .use_max_tr = true, }; - -# define register_preemptirqsoff(trace) register_tracer(&trace) -#else -# define register_preemptirqsoff(trace) do { } while (0) #endif

__init static int init_irqsoff_tracer(void) { - register_irqsoff(irqsoff_tracer); - register_preemptoff(preemptoff_tracer); - register_preemptirqsoff(preemptirqsoff_tracer); - - return 0; -} -core_initcall(init_irqsoff_tracer); -#endif /* IRQSOFF_TRACER || PREEMPTOFF_TRACER */ - -#ifndef CONFIG_IRQSOFF_TRACER -static inline void tracer_hardirqs_on(void) { } -static inline void tracer_hardirqs_off(void) { } -static inline void tracer_hardirqs_on_caller(unsigned long caller_addr) { } -static inline void tracer_hardirqs_off_caller(unsigned long caller_addr) { } +#ifdef CONFIG_IRQSOFF_TRACER + register_tracer(&irqsoff_tracer); #endif - -#ifndef CONFIG_PREEMPT_TRACER -static inline void tracer_preempt_on(unsigned long a0, unsigned long a1) { } -static inline void tracer_preempt_off(unsigned long a0, unsigned long a1) { } +#ifdef CONFIG_PREEMPT_TRACER + register_tracer(&preemptoff_tracer); #endif - -#if defined(CONFIG_TRACE_IRQFLAGS) && !defined(CONFIG_PROVE_LOCKING) -/* Per-cpu variable to prevent redundant calls when IRQs already off */ -static DEFINE_PER_CPU(int, tracing_irq_cpu); - -void trace_hardirqs_on(void) -{ - if (!this_cpu_read(tracing_irq_cpu)) - return; - - trace_irq_enable_rcuidle(CALLER_ADDR0, CALLER_ADDR1); - tracer_hardirqs_on(); - - this_cpu_write(tracing_irq_cpu, 0); -} -EXPORT_SYMBOL(trace_hardirqs_on); - -void trace_hardirqs_off(void) -{ - if (this_cpu_read(tracing_irq_cpu)) - return; - - this_cpu_write(tracing_irq_cpu, 1); - - trace_irq_disable_rcuidle(CALLER_ADDR0, CALLER_ADDR1); - tracer_hardirqs_off(); -} -EXPORT_SYMBOL(trace_hardirqs_off); - -__visible void trace_hardirqs_on_caller(unsigned long caller_addr) -{ - if (!this_cpu_read(tracing_irq_cpu)) - return; - - trace_irq_enable_rcuidle(CALLER_ADDR0, caller_addr); - tracer_hardirqs_on_caller(caller_addr); - - this_cpu_write(tracing_irq_cpu, 0); -} -EXPORT_SYMBOL(trace_hardirqs_on_caller); - -__visible void trace_hardirqs_off_caller(unsigned long caller_addr) -{ - if (this_cpu_read(tracing_irq_cpu)) - return; - - this_cpu_write(tracing_irq_cpu, 1); - - trace_irq_disable_rcuidle(CALLER_ADDR0, caller_addr); - tracer_hardirqs_off_caller(caller_addr); -} -EXPORT_SYMBOL(trace_hardirqs_off_caller); - -/* - * Stubs: - */ - -void trace_softirqs_on(unsigned long ip) -{ -} - -void trace_softirqs_off(unsigned long ip) -{ -} - -inline void print_irqtrace_events(struct task_struct *curr) -{ -} +#if defined(CONFIG_IRQSOFF_TRACER) && defined(CONFIG_PREEMPT_TRACER) + register_tracer(&preemptirqsoff_tracer); #endif

-#if defined(CONFIG_PREEMPT_TRACER) || \ - (defined(CONFIG_DEBUG_PREEMPT) && defined(CONFIG_PREEMPTIRQ_EVENTS)) -void trace_preempt_on(unsigned long a0, unsigned long a1) -{ - trace_preempt_enable_rcuidle(a0, a1); - tracer_preempt_on(a0, a1); -} - -void trace_preempt_off(unsigned long a0, unsigned long a1) -{ - trace_preempt_disable_rcuidle(a0, a1); - tracer_preempt_off(a0, a1); + return 0; } -#endif +core_initcall(init_irqsoff_tracer); +#endif /* IRQSOFF_TRACER || PREEMPTOFF_TRACER */ diff --git a/kernel/trace/trace_preemptirq.c b/kernel/trace/trace_preemptirq.c new file mode 100644 index 000000000000..dc01c7f4d326 --- /dev/null +++ b/kernel/trace/trace_preemptirq.c @@ -0,0 +1,71 @@ +/* + * preemptoff and irqoff tracepoints + * + * Copyright (C) Joel Fernandes (Google) joel@joelfernandes.org + */ + +#include <linux/kallsyms.h> +#include <linux/uaccess.h> +#include <linux/module.h> +#include <linux/ftrace.h> + +#define CREATE_TRACE_POINTS +#include <trace/events/preemptirq.h> + +#ifdef CONFIG_TRACE_IRQFLAGS +/* Per-cpu variable to prevent redundant calls when IRQs already off */ +static DEFINE_PER_CPU(int, tracing_irq_cpu); + +void trace_hardirqs_on(void) +{ + if (lockdep_recursing(current) || !this_cpu_read(tracing_irq_cpu)) + return; + + trace_irq_enable_rcuidle(CALLER_ADDR0, CALLER_ADDR1); + this_cpu_write(tracing_irq_cpu, 0); +} +EXPORT_SYMBOL(trace_hardirqs_on); + +void trace_hardirqs_off(void) +{ + if (lockdep_recursing(current) || this_cpu_read(tracing_irq_cpu)) + return; + + this_cpu_write(tracing_irq_cpu, 1); + trace_irq_disable_rcuidle(CALLER_ADDR0, CALLER_ADDR1); +} +EXPORT_SYMBOL(trace_hardirqs_off); + +__visible void trace_hardirqs_on_caller(unsigned long caller_addr) +{ + if (lockdep_recursing(current) || !this_cpu_read(tracing_irq_cpu)) + return; + + trace_irq_enable_rcuidle(CALLER_ADDR0, caller_addr); + this_cpu_write(tracing_irq_cpu, 0); +} +EXPORT_SYMBOL(trace_hardirqs_on_caller); + +__visible void trace_hardirqs_off_caller(unsigned long caller_addr) +{ + if (lockdep_recursing(current) || this_cpu_read(tracing_irq_cpu)) + return; + + this_cpu_write(tracing_irq_cpu, 1); + trace_irq_disable_rcuidle(CALLER_ADDR0, caller_addr); +} +EXPORT_SYMBOL(trace_hardirqs_off_caller); +#endif /* CONFIG_TRACE_IRQFLAGS */ + +#ifdef CONFIG_TRACE_PREEMPT_TOGGLE + +void trace_preempt_on(unsigned long a0, unsigned long a1) +{ + trace_preempt_enable_rcuidle(a0, a1); +} + +void trace_preempt_off(unsigned long a0, unsigned long a1) +{ + trace_preempt_disable_rcuidle(a0, a1); +} +#endif

Hi,

On Tue, May 29, 2018 at 05:04:59PM -0700, Joel Fernandes wrote:

From: "Joel Fernandes (Google)" joel@joelfernandes.org

In this patch we introduce a test module for simulating a long atomic section in the kernel which the preemptoff or irqsoff tracers can detect. This module is to be used only for test purposes and is default disabled.

Following is the expected output (only briefly shown) that can be parsed to verify that the tracers are working correctly. We will use this from the kselftests in future patches.

For the preemptoff tracer:

echo preemptoff > /d/tracing/current_tracer sleep 1 insmod ./test_atomic_sections.ko atomic_mode=preempt atomic_time=500000 sleep 1 bash-4.3# cat /d/tracing/trace preempt -1066 2...2 0us@: atomic_sect_run <-atomic_sect_run preempt -1066 2...2 500002us : atomic_sect_run <-atomic_sect_run preempt -1066 2...2 500004us : tracer_preempt_on <-atomic_sect_run preempt -1066 2...2 500012us : <stack trace> => kthread => ret_from_fork

For the irqsoff tracer:

echo irqsoff > /d/tracing/current_tracer sleep 1 insmod ./test_atomic_sections.ko atomic_mode=irq atomic_time=500000 sleep 1 bash-4.3# cat /d/tracing/trace irq dis -1069 1d..1 0us@: atomic_sect_run irq dis -1069 1d..1 500001us : atomic_sect_run irq dis -1069 1d..1 500002us : tracer_hardirqs_on <-atomic_sect_run irq dis -1069 1d..1 500005us : <stack trace> => ret_from_fork

Andy, previously made some suggestions to this patch. The updated version is below and I am planning to send it along with this series as v9. I have included it in advance below for your Review.

Andy, would you be Ok with adding your Reviewed-by to it?

---8<-----------------------

From: "Joel Fernandes (Google)" joel@joelfernandes.org Date: Wed, 16 May 2018 23:46:06 -0700 Subject: [PATCH v9 7/8] lib: Add module to simulate atomic sections for testing preemptoff tracers

In this patch we introduce a test module for simulating a long atomic section in the kernel which the preemptoff or irqsoff tracers can detect. This module is to be used only for test purposes and is default disabled.

Following is the expected output (only briefly shown) that can be parsed to verify that the tracers are working correctly. We will use this from the kselftests in future patches.

For the preemptoff tracer:

echo preemptoff > /d/tracing/current_tracer sleep 1 insmod ./test_atomic_sections.ko atomic_mode=preempt atomic_time=500000 sleep 1 bash-4.3# cat /d/tracing/trace preempt -1066 2...2 0us@: atomic_sect_run <-atomic_sect_run preempt -1066 2...2 500002us : atomic_sect_run <-atomic_sect_run preempt -1066 2...2 500004us : tracer_preempt_on <-atomic_sect_run preempt -1066 2...2 500012us : <stack trace> => kthread => ret_from_fork

For the irqsoff tracer:

echo irqsoff > /d/tracing/current_tracer sleep 1 insmod ./test_atomic_sections.ko atomic_mode=irq atomic_time=500000 sleep 1 bash-4.3# cat /d/tracing/trace irq dis -1069 1d..1 0us@: atomic_sect_run irq dis -1069 1d..1 500001us : atomic_sect_run irq dis -1069 1d..1 500002us : tracer_hardirqs_on <-atomic_sect_run irq dis -1069 1d..1 500005us : <stack trace> => ret_from_fork

Co-developed-by: Erick Reyes erickreyes@google.com Cc: Andy Shevchenko andriy.shevchenko@linux.intel.com Signed-off-by: Joel Fernandes (Google) joel@joelfernandes.org --- lib/Kconfig.debug | 8 ++++ lib/Makefile | 1 + lib/test_atomic_sections.c | 77 ++++++++++++++++++++++++++++++++++++++ 3 files changed, 86 insertions(+) create mode 100644 lib/test_atomic_sections.c

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index c40c7b734cd1..faebf0fe3bcf 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -1933,6 +1933,14 @@ config TEST_KMOD

If unsure, say N.

+config TEST_ATOMIC_SECTIONS + tristate "Simulate atomic sections for tracers to detect" + depends on m + help + Select this option to build a test module that can help test atomic + sections by simulating them with a duration supplied as a module + parameter. Preempt disable and irq disable modes can be requested. + config TEST_DEBUG_VIRTUAL tristate "Test CONFIG_DEBUG_VIRTUAL feature" depends on DEBUG_VIRTUAL diff --git a/lib/Makefile b/lib/Makefile index ce20696d5a92..e82cf5445b7b 100644 --- a/lib/Makefile +++ b/lib/Makefile @@ -46,6 +46,7 @@ obj-y += string_helpers.o obj-$(CONFIG_TEST_STRING_HELPERS) += test-string_helpers.o obj-y += hexdump.o obj-$(CONFIG_TEST_HEXDUMP) += test_hexdump.o +obj-$(CONFIG_TEST_ATOMIC_SECTIONS) += test_atomic_sections.o obj-y += kstrtox.o obj-$(CONFIG_FIND_BIT_BENCHMARK) += find_bit_benchmark.o obj-$(CONFIG_TEST_BPF) += test_bpf.o diff --git a/lib/test_atomic_sections.c b/lib/test_atomic_sections.c new file mode 100644 index 000000000000..1eef518f0974 --- /dev/null +++ b/lib/test_atomic_sections.c @@ -0,0 +1,77 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Atomic section emulation test module + * + * Emulates atomic sections by disabling IRQs or preemption + * and doing a busy wait for a specified amount of time. + * This can be used for testing of different atomic section + * tracers such as irqsoff tracers. + * + * (c) 2018. Google LLC + */ + +#include <linux/delay.h> +#include <linux/interrupt.h> +#include <linux/irq.h> +#include <linux/kernel.h> +#include <linux/kthread.h> +#include <linux/ktime.h> +#include <linux/module.h> +#include <linux/printk.h> +#include <linux/string.h> + +static ulong atomic_time = 100; +static char atomic_mode[10] = "irq"; + +module_param_named(atomic_time, atomic_time, ulong, S_IRUGO); +module_param_string(atomic_mode, atomic_mode, 10, S_IRUGO); +MODULE_PARM_DESC(atomic_time, "Period in microseconds (100 uS default)"); +MODULE_PARM_DESC(atomic_mode, "Mode of the test such as preempt or irq (default irq)"); + +static void busy_wait(ulong time) +{ + ktime_t start, end; + start = ktime_get(); + do { + end = ktime_get(); + if (kthread_should_stop()) + break; + } while (ktime_to_ns(ktime_sub(end, start)) < (time * 1000)); +} + +int atomic_sect_run(void *data) +{ + unsigned long flags; + + if (!strcmp(atomic_mode, "irq")) { + local_irq_save(flags); + busy_wait(atomic_time); + local_irq_restore(flags); + } else if (!strcmp(atomic_mode, "preempt")) { + preempt_disable(); + busy_wait(atomic_time); + preempt_enable(); + } + + return 0; +} + +static int __init atomic_sect_init(void) +{ + char task_name[50]; + struct task_struct *test_task; + + snprintf(task_name, sizeof(task_name), "%s_test", atomic_mode); + + test_task = kthread_run(atomic_sect_run, NULL, task_name); + return PTR_ERR_OR_ZERO(test_task); +} + +static void __exit atomic_sect_exit(void) +{ + return; +} + +module_init(atomic_sect_init) +module_exit(atomic_sect_exit) +MODULE_LICENSE("GPL v2");

On Tue, 2018-06-05 at 16:53 -0700, Joel Fernandes wrote:

(Resending since Andy wasn't on CC - sorry)

Andy, previously made some suggestions to this patch. The updated version is below and I am planning to send it along with this series as v9. I have included it in advance below for your Review.

Andy, would you be Ok with adding your Reviewed-by to it?

FWIW, Reviewed-by: Andy Shevchenko andriy.shevchenko@linux.intel.com

P.S. I'm not familiar with the topic so much to have any insights about implementation, though.

---8<-----------------------

From: "Joel Fernandes (Google)" joel@joelfernandes.org Date: Wed, 16 May 2018 23:46:06 -0700 Subject: [PATCH v9 7/8] lib: Add module to simulate atomic sections for testing preemptoff tracers

In this patch we introduce a test module for simulating a long atomic section in the kernel which the preemptoff or irqsoff tracers can detect. This module is to be used only for test purposes and is default disabled.

Following is the expected output (only briefly shown) that can be parsed to verify that the tracers are working correctly. We will use this from the kselftests in future patches.

For the preemptoff tracer:

echo preemptoff > /d/tracing/current_tracer sleep 1 insmod ./test_atomic_sections.ko atomic_mode=preempt atomic_time=500000 sleep 1 bash-4.3# cat /d/tracing/trace preempt -1066 2...2 0us@: atomic_sect_run <-atomic_sect_run preempt -1066 2...2 500002us : atomic_sect_run <-atomic_sect_run preempt -1066 2...2 500004us : tracer_preempt_on <-atomic_sect_run preempt -1066 2...2 500012us : <stack trace> => kthread => ret_from_fork

For the irqsoff tracer:

echo irqsoff > /d/tracing/current_tracer sleep 1 insmod ./test_atomic_sections.ko atomic_mode=irq atomic_time=500000 sleep 1 bash-4.3# cat /d/tracing/trace irq dis -1069 1d..1 0us@: atomic_sect_run irq dis -1069 1d..1 500001us : atomic_sect_run irq dis -1069 1d..1 500002us : tracer_hardirqs_on <-atomic_sect_run irq dis -1069 1d..1 500005us : <stack trace> => ret_from_fork

Co-developed-by: Erick Reyes erickreyes@google.com Cc: Andy Shevchenko andriy.shevchenko@linux.intel.com Signed-off-by: Joel Fernandes (Google) joel@joelfernandes.org

---

lib/Kconfig.debug | 8 ++++ lib/Makefile | 1 + lib/test_atomic_sections.c | 77 ++++++++++++++++++++++++++++++++++++++ 3 files changed, 86 insertions(+) create mode 100644 lib/test_atomic_sections.c

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index c40c7b734cd1..faebf0fe3bcf 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -1933,6 +1933,14 @@ config TEST_KMOD If unsure, say N. +config TEST_ATOMIC_SECTIONS

• tristate "Simulate atomic sections for tracers to detect"
• depends on m
• help

•  Select this option to build a test module that can help
  

test atomic

•  sections by simulating them with a duration supplied as a
  

module

•  parameter. Preempt disable and irq disable modes can be
  

requested.

config TEST_DEBUG_VIRTUAL tristate "Test CONFIG_DEBUG_VIRTUAL feature" depends on DEBUG_VIRTUAL diff --git a/lib/Makefile b/lib/Makefile index ce20696d5a92..e82cf5445b7b 100644 --- a/lib/Makefile +++ b/lib/Makefile @@ -46,6 +46,7 @@ obj-y += string_helpers.o obj-$(CONFIG_TEST_STRING_HELPERS) += test-string_helpers.o obj-y += hexdump.o obj-$(CONFIG_TEST_HEXDUMP) += test_hexdump.o +obj-$(CONFIG_TEST_ATOMIC_SECTIONS) += test_atomic_sections.o obj-y += kstrtox.o obj-$(CONFIG_FIND_BIT_BENCHMARK) += find_bit_benchmark.o obj-$(CONFIG_TEST_BPF) += test_bpf.o diff --git a/lib/test_atomic_sections.c b/lib/test_atomic_sections.c new file mode 100644 index 000000000000..1eef518f0974 --- /dev/null +++ b/lib/test_atomic_sections.c @@ -0,0 +1,77 @@ +// SPDX-License-Identifier: GPL-2.0 +/*

• • Atomic section emulation test module
• • Emulates atomic sections by disabling IRQs or preemption
• • and doing a busy wait for a specified amount of time.
• • This can be used for testing of different atomic section
• • tracers such as irqsoff tracers.
• • (c) 2018. Google LLC
• */

+#include <linux/delay.h> +#include <linux/interrupt.h> +#include <linux/irq.h> +#include <linux/kernel.h> +#include <linux/kthread.h> +#include <linux/ktime.h> +#include <linux/module.h> +#include <linux/printk.h> +#include <linux/string.h>

+static ulong atomic_time = 100; +static char atomic_mode[10] = "irq";

+module_param_named(atomic_time, atomic_time, ulong, S_IRUGO); +module_param_string(atomic_mode, atomic_mode, 10, S_IRUGO); +MODULE_PARM_DESC(atomic_time, "Period in microseconds (100 uS default)"); +MODULE_PARM_DESC(atomic_mode, "Mode of the test such as preempt or irq (default irq)");

+static void busy_wait(ulong time) +{

• ktime_t start, end;
• start = ktime_get();
• do {

• end = ktime_get();
  

• if (kthread_should_stop())
  

• 	break;
  

• } while (ktime_to_ns(ktime_sub(end, start)) < (time * 1000));

+}

+int atomic_sect_run(void *data) +{

• unsigned long flags;
• if (!strcmp(atomic_mode, "irq")) {

• local_irq_save(flags);
  

• busy_wait(atomic_time);
  

• local_irq_restore(flags);
  

• } else if (!strcmp(atomic_mode, "preempt")) {

• preempt_disable();
  

• busy_wait(atomic_time);
  

• preempt_enable();
  

• }
• return 0;

+}

+static int __init atomic_sect_init(void) +{

• char task_name[50];
• struct task_struct *test_task;
• snprintf(task_name, sizeof(task_name), "%s_test",

atomic_mode);

• test_task = kthread_run(atomic_sect_run, NULL, task_name);
• return PTR_ERR_OR_ZERO(test_task);

+}

+static void __exit atomic_sect_exit(void) +{

• return;

+}

+module_init(atomic_sect_init) +module_exit(atomic_sect_exit) +MODULE_LICENSE("GPL v2");

From: kbuild test robot fengguang.wu@intel.com

lib/test_atomic_sections.c:66:1-3: WARNING: PTR_ERR_OR_ZERO can be used

Use PTR_ERR_OR_ZERO rather than if(IS_ERR(...)) + PTR_ERR

Generated by: scripts/coccinelle/api/ptr_ret.cocci

Fixes: 3b0e47f0ade1 ("kselftests: Add tests for the preemptoff and irqsoff tracers") CC: Joel Fernandes (Google) joel@joelfernandes.org Signed-off-by: kbuild test robot fengguang.wu@intel.com ---

test_atomic_sections.c | 5 +---- 1 file changed, 1 insertion(+), 4 deletions(-)

--- a/lib/test_atomic_sections.c +++ b/lib/test_atomic_sections.c @@ -63,10 +63,7 @@ static int __init atomic_sect_init(void) snprintf(task_name, 50, "%s dis test", atomic_mode);

test_task = kthread_run((void*)atomic_sect_run, NULL, task_name); - if (IS_ERR(test_task)) - return PTR_ERR(test_task); - - return 0; + return PTR_ERR_OR_ZERO(test_task); }

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