Switching between stacks is only valid if we are tracing ourselves while on the irq_stack, so it is only valid when in current and non-preemptible context, otherwise is is just zeroed off.
Signed-off-by: Yang Shi yang.shi@linaro.org --- arch/arm64/kernel/stacktrace.c | 13 ++++++------- arch/arm64/kernel/traps.c | 11 ++++++++++- 2 files changed, 16 insertions(+), 8 deletions(-)
diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c index 12a18cb..d9751a4 100644 --- a/arch/arm64/kernel/stacktrace.c +++ b/arch/arm64/kernel/stacktrace.c @@ -44,14 +44,13 @@ int notrace unwind_frame(struct task_struct *tsk, struct stackframe *frame) unsigned long irq_stack_ptr;
/* - * Use raw_smp_processor_id() to avoid false-positives from - * CONFIG_DEBUG_PREEMPT. get_wchan() calls unwind_frame() on sleeping - * task stacks, we can be pre-empted in this case, so - * {raw_,}smp_processor_id() may give us the wrong value. Sleeping - * tasks can't ever be on an interrupt stack, so regardless of cpu, - * the checks will always fail. + * Switching between stacks is valid when tracing current and in + * non-preemptible context. */ - irq_stack_ptr = IRQ_STACK_PTR(raw_smp_processor_id()); + if (tsk == current && !preemptible()) + irq_stack_ptr = IRQ_STACK_PTR(smp_processor_id()); + else + irq_stack_ptr = 0;
low = frame->sp; /* irq stacks are not THREAD_SIZE aligned */ diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c index cbedd72..7d8db3a 100644 --- a/arch/arm64/kernel/traps.c +++ b/arch/arm64/kernel/traps.c @@ -146,9 +146,18 @@ static void dump_instr(const char *lvl, struct pt_regs *regs) static void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk) { struct stackframe frame; - unsigned long irq_stack_ptr = IRQ_STACK_PTR(smp_processor_id()); + unsigned long irq_stack_ptr; int skip;
+ /* + * Switching between stacks is valid when tracing current and in + * non-preemptible context. + */ + if (tsk == current && !preemptible()) + irq_stack_ptr = IRQ_STACK_PTR(smp_processor_id()); + else + irq_stack_ptr = 0; + pr_debug("%s(regs = %p tsk = %p)\n", __func__, regs, tsk);
if (!tsk)
Hi!
On 11/02/16 21:53, Yang Shi wrote:
Switching between stacks is only valid if we are tracing ourselves while on the irq_stack, so it is only valid when in current and non-preemptible context, otherwise is is just zeroed off.
Given it was picked up with CONFIG_DEBUG_PREEMPT:
Fixes: 132cd887b5c5 ("arm64: Modify stack trace and dump for use with irq_stack")
Signed-off-by: Yang Shi yang.shi@linaro.org
arch/arm64/kernel/stacktrace.c | 13 ++++++------- arch/arm64/kernel/traps.c | 11 ++++++++++- 2 files changed, 16 insertions(+), 8 deletions(-)
diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c index 12a18cb..d9751a4 100644 --- a/arch/arm64/kernel/stacktrace.c +++ b/arch/arm64/kernel/stacktrace.c @@ -44,14 +44,13 @@ int notrace unwind_frame(struct task_struct *tsk, struct stackframe *frame) unsigned long irq_stack_ptr; /*
* Use raw_smp_processor_id() to avoid false-positives from* CONFIG_DEBUG_PREEMPT. get_wchan() calls unwind_frame() on sleeping* task stacks, we can be pre-empted in this case, so* {raw_,}smp_processor_id() may give us the wrong value. Sleeping* tasks can't ever be on an interrupt stack, so regardless of cpu,* the checks will always fail.
* Switching between stacks is valid when tracing current and in* non-preemptible context.
- irq_stack_ptr = IRQ_STACK_PTR(raw_smp_processor_id());
- if (tsk == current && !preemptible())
irq_stack_ptr = IRQ_STACK_PTR(smp_processor_id());- else
irq_stack_ptr = 0;low = frame->sp; /* irq stacks are not THREAD_SIZE aligned */ diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c index cbedd72..7d8db3a 100644 --- a/arch/arm64/kernel/traps.c +++ b/arch/arm64/kernel/traps.c @@ -146,9 +146,18 @@ static void dump_instr(const char *lvl, struct pt_regs *regs) static void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk) { struct stackframe frame;
- unsigned long irq_stack_ptr = IRQ_STACK_PTR(smp_processor_id());
- unsigned long irq_stack_ptr; int skip;
- /*
* Switching between stacks is valid when tracing current and in
Nit: Two spaces: "between[ ][ ]stacks"
* non-preemptible context.*/- if (tsk == current && !preemptible())
irq_stack_ptr = IRQ_STACK_PTR(smp_processor_id());- else
irq_stack_ptr = 0;- pr_debug("%s(regs = %p tsk = %p)\n", __func__, regs, tsk);
if (!tsk)
Neither file includes 'linux/preempt.h' for the definition of preemptible(). (I can't talk: I should have included smp.h for smp_processor_id())
Acked-by: James Morse james.morse@arm.com Tested-by: James Morse james.morse@arm.com
Thanks!
James
On 2/12/2016 5:47 AM, James Morse wrote:
Hi!
On 11/02/16 21:53, Yang Shi wrote:
Switching between stacks is only valid if we are tracing ourselves while on the irq_stack, so it is only valid when in current and non-preemptible context, otherwise is is just zeroed off.
Given it was picked up with CONFIG_DEBUG_PREEMPT:
Fixes: 132cd887b5c5 ("arm64: Modify stack trace and dump for use with irq_stack")
Wii add in v2.
Signed-off-by: Yang Shi yang.shi@linaro.org
arch/arm64/kernel/stacktrace.c | 13 ++++++------- arch/arm64/kernel/traps.c | 11 ++++++++++- 2 files changed, 16 insertions(+), 8 deletions(-)
diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c index 12a18cb..d9751a4 100644 --- a/arch/arm64/kernel/stacktrace.c +++ b/arch/arm64/kernel/stacktrace.c @@ -44,14 +44,13 @@ int notrace unwind_frame(struct task_struct *tsk, struct stackframe *frame) unsigned long irq_stack_ptr;
/*
* Use raw_smp_processor_id() to avoid false-positives from* CONFIG_DEBUG_PREEMPT. get_wchan() calls unwind_frame() on sleeping* task stacks, we can be pre-empted in this case, so* {raw_,}smp_processor_id() may give us the wrong value. Sleeping* tasks can't ever be on an interrupt stack, so regardless of cpu,* the checks will always fail.
* Switching between stacks is valid when tracing current and in* non-preemptible context.
- irq_stack_ptr = IRQ_STACK_PTR(raw_smp_processor_id());
if (tsk == current && !preemptible())
irq_stack_ptr = IRQ_STACK_PTR(smp_processor_id());else
irq_stack_ptr = 0;low = frame->sp; /* irq stacks are not THREAD_SIZE aligned */
diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c index cbedd72..7d8db3a 100644 --- a/arch/arm64/kernel/traps.c +++ b/arch/arm64/kernel/traps.c @@ -146,9 +146,18 @@ static void dump_instr(const char *lvl, struct pt_regs *regs) static void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk) { struct stackframe frame;
- unsigned long irq_stack_ptr = IRQ_STACK_PTR(smp_processor_id());
unsigned long irq_stack_ptr; int skip;
/*
* Switching between stacks is valid when tracing current and inNit: Two spaces: "between[ ][ ]stacks"
Will fix in v2.
* non-preemptible context.*/if (tsk == current && !preemptible())
irq_stack_ptr = IRQ_STACK_PTR(smp_processor_id());else
irq_stack_ptr = 0;pr_debug("%s(regs = %p tsk = %p)\n", __func__, regs, tsk);
if (!tsk)
Neither file includes 'linux/preempt.h' for the definition of preemptible(). (I can't talk: I should have included smp.h for smp_processor_id())
I tried to build the kernel with preempt and without preempt, both works. And, I saw arch/arm64/include/asm/Kbuild has:
generic-y += preempt.h
So, it sounds preempt.h has been included by default.
Thanks, Yang
Acked-by: James Morse james.morse@arm.com Tested-by: James Morse james.morse@arm.com
Thanks!
James
On Fri, Feb 12, 2016 at 09:38:51AM -0800, Shi, Yang wrote:
On 2/12/2016 5:47 AM, James Morse wrote:
On 11/02/16 21:53, Yang Shi wrote:
Switching between stacks is only valid if we are tracing ourselves while on the irq_stack, so it is only valid when in current and non-preemptible context, otherwise is is just zeroed off.
Given it was picked up with CONFIG_DEBUG_PREEMPT:
Fixes: 132cd887b5c5 ("arm64: Modify stack trace and dump for use with irq_stack")
Wii add in v2.
I already queued the patch with this and the whitespace fix, so no need for a v2.
Will
On 2/12/2016 9:41 AM, Will Deacon wrote:
On Fri, Feb 12, 2016 at 09:38:51AM -0800, Shi, Yang wrote:
On 2/12/2016 5:47 AM, James Morse wrote:
On 11/02/16 21:53, Yang Shi wrote:
Switching between stacks is only valid if we are tracing ourselves while on the irq_stack, so it is only valid when in current and non-preemptible context, otherwise is is just zeroed off.
Given it was picked up with CONFIG_DEBUG_PREEMPT:
Fixes: 132cd887b5c5 ("arm64: Modify stack trace and dump for use with irq_stack")
Wii add in v2.
I already queued the patch with this and the whitespace fix, so no need for a v2.
Thanks so much.
Yang
Will
On 2/12/2016 9:38 AM, Shi, Yang wrote:
On 2/12/2016 5:47 AM, James Morse wrote:
Hi!
On 11/02/16 21:53, Yang Shi wrote:
Switching between stacks is only valid if we are tracing ourselves while on the irq_stack, so it is only valid when in current and non-preemptible context, otherwise is is just zeroed off.
Given it was picked up with CONFIG_DEBUG_PREEMPT:
Fixes: 132cd887b5c5 ("arm64: Modify stack trace and dump for use with irq_stack")
Wii add in v2.
Signed-off-by: Yang Shi yang.shi@linaro.org
arch/arm64/kernel/stacktrace.c | 13 ++++++------- arch/arm64/kernel/traps.c | 11 ++++++++++- 2 files changed, 16 insertions(+), 8 deletions(-)
diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c index 12a18cb..d9751a4 100644 --- a/arch/arm64/kernel/stacktrace.c +++ b/arch/arm64/kernel/stacktrace.c @@ -44,14 +44,13 @@ int notrace unwind_frame(struct task_struct *tsk, struct stackframe *frame) unsigned long irq_stack_ptr;
/*
* Use raw_smp_processor_id() to avoid false-positives from* CONFIG_DEBUG_PREEMPT. get_wchan() calls unwind_frame() onsleeping
* task stacks, we can be pre-empted in this case, so* {raw_,}smp_processor_id() may give us the wrong value. Sleeping* tasks can't ever be on an interrupt stack, so regardless of cpu,* the checks will always fail.
* Switching between stacks is valid when tracing current and in* non-preemptible context. */
- irq_stack_ptr = IRQ_STACK_PTR(raw_smp_processor_id());
if (tsk == current && !preemptible())
irq_stack_ptr = IRQ_STACK_PTR(smp_processor_id());else
irq_stack_ptr = 0; low = frame->sp; /* irq stacks are not THREAD_SIZE aligned */diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c index cbedd72..7d8db3a 100644 --- a/arch/arm64/kernel/traps.c +++ b/arch/arm64/kernel/traps.c @@ -146,9 +146,18 @@ static void dump_instr(const char *lvl, struct pt_regs *regs) static void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk) { struct stackframe frame;
- unsigned long irq_stack_ptr = IRQ_STACK_PTR(smp_processor_id());
unsigned long irq_stack_ptr; int skip;
/*
* Switching between stacks is valid when tracing current and inNit: Two spaces: "between[ ][ ]stacks"
Will fix in v2.
* non-preemptible context.*/if (tsk == current && !preemptible())
irq_stack_ptr = IRQ_STACK_PTR(smp_processor_id());else
irq_stack_ptr = 0;pr_debug("%s(regs = %p tsk = %p)\n", __func__, regs, tsk); if (!tsk)Neither file includes 'linux/preempt.h' for the definition of preemptible(). (I can't talk: I should have included smp.h for smp_processor_id())
I tried to build the kernel with preempt and without preempt, both works. And, I saw arch/arm64/include/asm/Kbuild has:
generic-y += preempt.h
So, it sounds preempt.h has been included by default.
In addition, linux/sched.h, which is included by both traps.c and stacktrace.c, includes preempt.h already.
Yang
Thanks, Yang
Acked-by: James Morse james.morse@arm.com Tested-by: James Morse james.morse@arm.com
Thanks!
James
linaro-kernel@lists.linaro.org
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