From: Peter Zijlstra peterz@infradead.org
[ Upstream commit 5a5d7e9badd2cb8065db171961bd30bd3595e4b6 ]
In order to avoid WARN/BUG from generating nested or even recursive warnings, force rcu_is_watching() true during WARN/lockdep_rcu_suspicious().
Notably things like unwinding the stack can trigger rcu_dereference() warnings, which then triggers more unwinding which then triggers more warnings etc..
Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Signed-off-by: Ingo Molnar mingo@kernel.org Link: https://lore.kernel.org/r/20230126151323.408156109@infradead.org Signed-off-by: Sasha Levin sashal@kernel.org --- include/linux/context_tracking.h | 27 +++++++++++++++++++++++++++ kernel/locking/lockdep.c | 3 +++ kernel/panic.c | 5 +++++ lib/bug.c | 15 ++++++++++++++- 4 files changed, 49 insertions(+), 1 deletion(-)
diff --git a/include/linux/context_tracking.h b/include/linux/context_tracking.h index dcef4a9e4d63e..d4afa8508a806 100644 --- a/include/linux/context_tracking.h +++ b/include/linux/context_tracking.h @@ -130,9 +130,36 @@ static __always_inline unsigned long ct_state_inc(int incby) return arch_atomic_add_return(incby, this_cpu_ptr(&context_tracking.state)); }
+static __always_inline bool warn_rcu_enter(void) +{ + bool ret = false; + + /* + * Horrible hack to shut up recursive RCU isn't watching fail since + * lots of the actual reporting also relies on RCU. + */ + preempt_disable_notrace(); + if (rcu_dynticks_curr_cpu_in_eqs()) { + ret = true; + ct_state_inc(RCU_DYNTICKS_IDX); + } + + return ret; +} + +static __always_inline void warn_rcu_exit(bool rcu) +{ + if (rcu) + ct_state_inc(RCU_DYNTICKS_IDX); + preempt_enable_notrace(); +} + #else static inline void ct_idle_enter(void) { } static inline void ct_idle_exit(void) { } + +static __always_inline bool warn_rcu_enter(void) { return false; } +static __always_inline void warn_rcu_exit(bool rcu) { } #endif /* !CONFIG_CONTEXT_TRACKING_IDLE */
#endif diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c index e3375bc40dadc..50d4863974e7a 100644 --- a/kernel/locking/lockdep.c +++ b/kernel/locking/lockdep.c @@ -55,6 +55,7 @@ #include <linux/rcupdate.h> #include <linux/kprobes.h> #include <linux/lockdep.h> +#include <linux/context_tracking.h>
#include <asm/sections.h>
@@ -6555,6 +6556,7 @@ void lockdep_rcu_suspicious(const char *file, const int line, const char *s) { struct task_struct *curr = current; int dl = READ_ONCE(debug_locks); + bool rcu = warn_rcu_enter();
/* Note: the following can be executed concurrently, so be careful. */ pr_warn("\n"); @@ -6595,5 +6597,6 @@ void lockdep_rcu_suspicious(const char *file, const int line, const char *s) lockdep_print_held_locks(curr); pr_warn("\nstack backtrace:\n"); dump_stack(); + warn_rcu_exit(rcu); } EXPORT_SYMBOL_GPL(lockdep_rcu_suspicious); diff --git a/kernel/panic.c b/kernel/panic.c index 7834c9854e026..5864f356ee576 100644 --- a/kernel/panic.c +++ b/kernel/panic.c @@ -33,6 +33,7 @@ #include <linux/ratelimit.h> #include <linux/debugfs.h> #include <linux/sysfs.h> +#include <linux/context_tracking.h> #include <trace/events/error_report.h> #include <asm/sections.h>
@@ -678,6 +679,7 @@ void __warn(const char *file, int line, void *caller, unsigned taint, void warn_slowpath_fmt(const char *file, int line, unsigned taint, const char *fmt, ...) { + bool rcu = warn_rcu_enter(); struct warn_args args;
pr_warn(CUT_HERE); @@ -692,11 +694,13 @@ void warn_slowpath_fmt(const char *file, int line, unsigned taint, va_start(args.args, fmt); __warn(file, line, __builtin_return_address(0), taint, NULL, &args); va_end(args.args); + warn_rcu_exit(rcu); } EXPORT_SYMBOL(warn_slowpath_fmt); #else void __warn_printk(const char *fmt, ...) { + bool rcu = warn_rcu_enter(); va_list args;
pr_warn(CUT_HERE); @@ -704,6 +708,7 @@ void __warn_printk(const char *fmt, ...) va_start(args, fmt); vprintk(fmt, args); va_end(args); + warn_rcu_exit(rcu); } EXPORT_SYMBOL(__warn_printk); #endif diff --git a/lib/bug.c b/lib/bug.c index c223a2575b721..e0ff219899902 100644 --- a/lib/bug.c +++ b/lib/bug.c @@ -47,6 +47,7 @@ #include <linux/sched.h> #include <linux/rculist.h> #include <linux/ftrace.h> +#include <linux/context_tracking.h>
extern struct bug_entry __start___bug_table[], __stop___bug_table[];
@@ -153,7 +154,7 @@ struct bug_entry *find_bug(unsigned long bugaddr) return module_find_bug(bugaddr); }
-enum bug_trap_type report_bug(unsigned long bugaddr, struct pt_regs *regs) +static enum bug_trap_type __report_bug(unsigned long bugaddr, struct pt_regs *regs) { struct bug_entry *bug; const char *file; @@ -209,6 +210,18 @@ enum bug_trap_type report_bug(unsigned long bugaddr, struct pt_regs *regs) return BUG_TRAP_TYPE_BUG; }
+enum bug_trap_type report_bug(unsigned long bugaddr, struct pt_regs *regs) +{ + enum bug_trap_type ret; + bool rcu = false; + + rcu = warn_rcu_enter(); + ret = __report_bug(bugaddr, regs); + warn_rcu_exit(rcu); + + return ret; +} + static void clear_once_table(struct bug_entry *start, struct bug_entry *end) { struct bug_entry *bug;