From 03889384cee7a198a79447c1ea6aca2c8e54d155 Mon Sep 17 00:00:00 2001 From: Steven Rostedt Date: Fri, 11 Dec 2009 09:48:22 -0500 Subject: tracing: Add trace_dump_stack() I've been asked a few times about how to find out what is calling some location in the kernel. One way is to use dynamic function tracing and implement the func_stack_trace. But this only finds out who is calling a particular function. It does not tell you who is calling that function and entering a specific if conditional. I have myself implemented a quick version of trace_dump_stack() for this purpose a few times, and just needed it now. This is when I realized that this would be a good tool to have in the kernel like trace_printk(). Using trace_dump_stack() is similar to dump_stack() except that it writes to the trace buffer instead and can be used in critical locations. For example: @@ -5485,8 +5485,12 @@ need_resched_nonpreemptible: if (prev->state && !(preempt_count() & PREEMPT_ACTIVE)) { if (unlikely(signal_pending_state(prev->state, prev))) prev->state = TASK_RUNNING; - else + else { deactivate_task(rq, prev, 1); + trace_printk("Deactivating task %s:%d\n", + prev->comm, prev->pid); + trace_dump_stack(); + } switch_count = &prev->nvcsw; } Produces: <...>-3249 [001] 296.105269: schedule: Deactivating task ntpd:3249 <...>-3249 [001] 296.105270: => schedule => schedule_hrtimeout_range => poll_schedule_timeout => do_select => core_sys_select => sys_select => system_call_fastpath Signed-off-by: Steven Rostedt --- include/linux/kernel.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'include/linux/kernel.h') diff --git a/include/linux/kernel.h b/include/linux/kernel.h index 3fa4c590cf12..5ad4199fb073 100644 --- a/include/linux/kernel.h +++ b/include/linux/kernel.h @@ -492,6 +492,8 @@ extern int __trace_printk(unsigned long ip, const char *fmt, ...) __attribute__ ((format (printf, 2, 3))); +extern void trace_dump_stack(void); + /* * The double __builtin_constant_p is because gcc will give us an error * if we try to allocate the static variable to fmt if it is not a -- cgit v1.2.3 From e36c54582c6f14adc9e10473e2aec2cc4f0acc03 Mon Sep 17 00:00:00 2001 From: Steven Rostedt Date: Mon, 14 Dec 2009 15:58:33 -0500 Subject: tracing: Fix return of trace_dump_stack() The trace_dump_stack() returned a value for a void function. Also, added the missing stub for trace_dump_stack() when tracing is not configured. Reported-by: Ingo Molnar LKML-Reference: <20091214162713.GA31060@elte.hu> Signed-off-by: Steven Rostedt Signed-off-by: Ingo Molnar --- include/linux/kernel.h | 1 + kernel/trace/trace.c | 2 +- 2 files changed, 2 insertions(+), 1 deletion(-) (limited to 'include/linux/kernel.h') diff --git a/include/linux/kernel.h b/include/linux/kernel.h index 5ad4199fb073..f1dc752da0d2 100644 --- a/include/linux/kernel.h +++ b/include/linux/kernel.h @@ -527,6 +527,7 @@ trace_printk(const char *fmt, ...) __attribute__ ((format (printf, 1, 2))); static inline void tracing_start(void) { } static inline void tracing_stop(void) { } static inline void ftrace_off_permanent(void) { } +static inline void trace_dump_stack(void) { } static inline int trace_printk(const char *fmt, ...) { diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index bd7b969a729a..ee61915935d5 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -1158,7 +1158,7 @@ void trace_dump_stack(void) unsigned long flags; if (tracing_disabled || tracing_selftest_running) - return 0; + return; local_save_flags(flags); -- cgit v1.2.3 From d894837f23f491aa7ed167aae767fc07cfe6e6e6 Mon Sep 17 00:00:00 2001 From: Simon Kagstrom Date: Wed, 23 Dec 2009 11:08:18 +0100 Subject: sched: might_sleep(): Make file parameter const char * Fixes a warning when building with g++: warning: deprecated conversion from string constant to 'char*' And the file parameter use is constant, so mark it as such. Signed-off-by: Simon Kagstrom Cc: peterz@infradead.org LKML-Reference: <20091223110818.442d848e@marrow.netinsight.se> Signed-off-by: Ingo Molnar --- include/linux/kernel.h | 5 +++-- kernel/sched.c | 2 +- 2 files changed, 4 insertions(+), 3 deletions(-) (limited to 'include/linux/kernel.h') diff --git a/include/linux/kernel.h b/include/linux/kernel.h index 3fc9f5aab5f8..785d7d1099d4 100644 --- a/include/linux/kernel.h +++ b/include/linux/kernel.h @@ -124,7 +124,7 @@ extern int _cond_resched(void); #endif #ifdef CONFIG_DEBUG_SPINLOCK_SLEEP - void __might_sleep(char *file, int line, int preempt_offset); + void __might_sleep(const char *file, int line, int preempt_offset); /** * might_sleep - annotation for functions that can sleep * @@ -138,7 +138,8 @@ extern int _cond_resched(void); # define might_sleep() \ do { __might_sleep(__FILE__, __LINE__, 0); might_resched(); } while (0) #else - static inline void __might_sleep(char *file, int line, int preempt_offset) { } + static inline void __might_sleep(const char *file, int line, + int preempt_offset) { } # define might_sleep() do { might_resched(); } while (0) #endif diff --git a/kernel/sched.c b/kernel/sched.c index c535cc4f6428..64298a52eaa6 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -9694,7 +9694,7 @@ static inline int preempt_count_equals(int preempt_offset) return (nested == PREEMPT_INATOMIC_BASE + preempt_offset); } -void __might_sleep(char *file, int line, int preempt_offset) +void __might_sleep(const char *file, int line, int preempt_offset) { #ifdef in_atomic static unsigned long prev_jiffy; /* ratelimiting */ -- cgit v1.2.3 From cc8ef6eb21e964b1c5eb97b2d0e8ac9893e1bf86 Mon Sep 17 00:00:00 2001 From: Roland Dreier Date: Fri, 15 Jan 2010 17:01:22 -0800 Subject: kernel.h: add BUILD_BUG_ON_NOT_POWER_OF_2() Add BUILD_BUG_ON_NOT_POWER_OF_2() When code relies on a constant being a power of 2: #define FOO 512 /* must be a power of 2 */ it would be nice to be able to do: BUILD_BUG_ON(!is_power_of_2(FOO)); However applying an inline function does not result in a compile-time constant that can be used with BUILD_BUG_ON(), so trying that gives results in: error: bit-field '' width not an integer constant As suggested by akpm, rather than monkeying around with is_power_of_2() and risking gcc warts about constant expressions, just create a macro BUILD_BUG_ON_NOT_POWER_OF_2() to encapsulate this common requirement. Signed-off-by: Roland Dreier Cc: Bart Van Assche Cc: David Dillow Cc: "Robert P. J. Day" Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/kernel.h | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'include/linux/kernel.h') diff --git a/include/linux/kernel.h b/include/linux/kernel.h index 3fc9f5aab5f8..328bca609b9b 100644 --- a/include/linux/kernel.h +++ b/include/linux/kernel.h @@ -734,6 +734,10 @@ struct sysinfo { /* Force a compilation error if condition is constant and true */ #define MAYBE_BUILD_BUG_ON(cond) ((void)sizeof(char[1 - 2 * !!(cond)])) +/* Force a compilation error if a constant expression is not a power of 2 */ +#define BUILD_BUG_ON_NOT_POWER_OF_2(n) \ + BUILD_BUG_ON((n) == 0 || (((n) & ((n) - 1)) != 0)) + /* Force a compilation error if condition is true, but also produce a result (of value 0 and type size_t), so the expression can be used e.g. in a structure initializer (or where-ever else comma expressions -- cgit v1.2.3 From 9b3be9f99203d9a400e8547f0e80f1d8f8e5738c Mon Sep 17 00:00:00 2001 From: Yinghai Lu Date: Wed, 10 Feb 2010 01:20:29 -0800 Subject: Move round_up/down to kernel.h ... in preparation of moving early_res to kernel/. Signed-off-by: Yinghai Lu LKML-Reference: <1265793639-15071-26-git-send-email-yinghai@kernel.org> Signed-off-by: H. Peter Anvin --- arch/x86/include/asm/proto.h | 10 ---------- include/linux/kernel.h | 10 ++++++++++ 2 files changed, 10 insertions(+), 10 deletions(-) (limited to 'include/linux/kernel.h') diff --git a/arch/x86/include/asm/proto.h b/arch/x86/include/asm/proto.h index 4009f6534f52..6f414ed88620 100644 --- a/arch/x86/include/asm/proto.h +++ b/arch/x86/include/asm/proto.h @@ -23,14 +23,4 @@ extern int reboot_force; long do_arch_prctl(struct task_struct *task, int code, unsigned long addr); -/* - * This looks more complex than it should be. But we need to - * get the type for the ~ right in round_down (it needs to be - * as wide as the result!), and we want to evaluate the macro - * arguments just once each. - */ -#define __round_mask(x,y) ((__typeof__(x))((y)-1)) -#define round_up(x,y) ((((x)-1) | __round_mask(x,y))+1) -#define round_down(x,y) ((x) & ~__round_mask(x,y)) - #endif /* _ASM_X86_PROTO_H */ diff --git a/include/linux/kernel.h b/include/linux/kernel.h index 328bca609b9b..d45e372fad81 100644 --- a/include/linux/kernel.h +++ b/include/linux/kernel.h @@ -44,6 +44,16 @@ extern const char linux_proc_banner[]; #define ARRAY_SIZE(arr) (sizeof(arr) / sizeof((arr)[0]) + __must_be_array(arr)) +/* + * This looks more complex than it should be. But we need to + * get the type for the ~ right in round_down (it needs to be + * as wide as the result!), and we want to evaluate the macro + * arguments just once each. + */ +#define __round_mask(x, y) ((__typeof__(x))((y)-1)) +#define round_up(x, y) ((((x)-1) | __round_mask(x, y))+1) +#define round_down(x, y) ((x) & ~__round_mask(x, y)) + #define FIELD_SIZEOF(t, f) (sizeof(((t*)0)->f)) #define DIV_ROUND_UP(n,d) (((n) + (d) - 1) / (d)) #define roundup(x, y) ((((x) + ((y) - 1)) / (y)) * (y)) -- cgit v1.2.3