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 + 1 file changed, 1 insertion(+) (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, ...) { -- cgit v1.2.3 From 00b55864bb37200d7f05143c44f5e2edfc8c4578 Mon Sep 17 00:00:00 2001 From: Joe Perches Date: Mon, 14 Dec 2009 18:00:14 -0800 Subject: dynamic_debug.h/kernel.h: Remove KBUILD_MODNAME from dynamic_pr_debug If CONFIG_DYNAMIC_DEBUG is enabled and a source file has: #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt #include dynamic_debug.h will duplicate KBUILD_MODNAME in the output string. Remove the use of KBUILD_MODNAME from the output format string generated by dynamic_debug.h If CONFIG_DYNAMIC_DEBUG is not enabled, no compile-time check is done to printk/dev_printk arguments. Add it. Signed-off-by: Joe Perches Cc: Jason Baron Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/kernel.h | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) (limited to 'include/linux/kernel.h') diff --git a/include/linux/kernel.h b/include/linux/kernel.h index 3fa4c590cf12..a93cdd031aee 100644 --- a/include/linux/kernel.h +++ b/include/linux/kernel.h @@ -397,9 +397,8 @@ static inline char *pack_hex_byte(char *buf, u8 byte) printk(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__) #elif defined(CONFIG_DYNAMIC_DEBUG) /* dynamic_pr_debug() uses pr_fmt() internally so we don't need it here */ -#define pr_debug(fmt, ...) do { \ - dynamic_pr_debug(fmt, ##__VA_ARGS__); \ - } while (0) +#define pr_debug(fmt, ...) \ + dynamic_pr_debug(fmt, ##__VA_ARGS__) #else #define pr_debug(fmt, ...) \ ({ if (0) printk(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__); 0; }) -- cgit v1.2.3 From 0b2749aa6ca40ff3fe12ebb3fdf010ebad2e9085 Mon Sep 17 00:00:00 2001 From: Joe Perches Date: Mon, 14 Dec 2009 18:00:19 -0800 Subject: kernel.h: remove initialization of bool in printk_once Don't initialize __print_once. Invert the test to reduce initialized data. defconfig before: $size vmlinux text data bss dec hex filename 6976022 679572 1359668 9015262 898fde vmlinux defconfig after: $size vmlinux text data bss dec hex filename 6976006 679508 1359700 9015214 898fae vmlinux Signed-off-by: Joe Perches Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/kernel.h | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) (limited to 'include/linux/kernel.h') diff --git a/include/linux/kernel.h b/include/linux/kernel.h index a93cdd031aee..910db75b1a72 100644 --- a/include/linux/kernel.h +++ b/include/linux/kernel.h @@ -251,10 +251,10 @@ extern int printk_delay_msec; * Print a one-time message (analogous to WARN_ONCE() et al): */ #define printk_once(x...) ({ \ - static bool __print_once = true; \ + static bool __print_once; \ \ - if (__print_once) { \ - __print_once = false; \ + if (!__print_once) { \ + __print_once = true; \ printk(x); \ } \ }) -- cgit v1.2.3 From 8a64f336bc1d4aa203b138d29d5a9c414a9fbb47 Mon Sep 17 00:00:00 2001 From: Joe Perches Date: Mon, 14 Dec 2009 18:00:25 -0800 Subject: kernel.h: add printk_ratelimited and pr__rl Add a printk_ratelimited statement expression macro that uses a per-call ratelimit_state so that multiple subsystems output messages are not suppressed by a global __ratelimit state. [akpm@linux-foundation.org: coding-style fixes] [akpm@linux-foundation.org: s/_rl/_ratelimited/g] Signed-off-by: Joe Perches Cc: Naohiro Ooiwa Cc: Ingo Molnar Cc: Hiroshi Shimamoto Cc: Peter Zijlstra Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/kernel.h | 44 ++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 44 insertions(+) (limited to 'include/linux/kernel.h') diff --git a/include/linux/kernel.h b/include/linux/kernel.h index 910db75b1a72..4d9c916d06d9 100644 --- a/include/linux/kernel.h +++ b/include/linux/kernel.h @@ -404,6 +404,50 @@ static inline char *pack_hex_byte(char *buf, u8 byte) ({ if (0) printk(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__); 0; }) #endif +/* + * ratelimited messages with local ratelimit_state, + * no local ratelimit_state used in the !PRINTK case + */ +#ifdef CONFIG_PRINTK +#define printk_ratelimited(fmt, ...) ({ \ + static struct ratelimit_state _rs = { \ + .interval = DEFAULT_RATELIMIT_INTERVAL, \ + .burst = DEFAULT_RATELIMIT_BURST, \ + }; \ + \ + if (!__ratelimit(&_rs)) \ + printk(fmt, ##__VA_ARGS__); \ +}) +#else +/* No effect, but we still get type checking even in the !PRINTK case: */ +#define printk_ratelimited printk +#endif + +#define pr_emerg_ratelimited(fmt, ...) \ + printk_ratelimited(KERN_EMERG pr_fmt(fmt), ##__VA_ARGS__) +#define pr_alert_ratelimited(fmt, ...) \ + printk_ratelimited(KERN_ALERT pr_fmt(fmt), ##__VA_ARGS__) +#define pr_crit_ratelimited(fmt, ...) \ + printk_ratelimited(KERN_CRIT pr_fmt(fmt), ##__VA_ARGS__) +#define pr_err_ratelimited(fmt, ...) \ + printk_ratelimited(KERN_ERR pr_fmt(fmt), ##__VA_ARGS__) +#define pr_warning_ratelimited(fmt, ...) \ + printk_ratelimited(KERN_WARNING pr_fmt(fmt), ##__VA_ARGS__) +#define pr_notice_ratelimited(fmt, ...) \ + printk_ratelimited(KERN_NOTICE pr_fmt(fmt), ##__VA_ARGS__) +#define pr_info_ratelimited(fmt, ...) \ + printk_ratelimited(KERN_INFO pr_fmt(fmt), ##__VA_ARGS__) +/* no pr_cont_ratelimited, don't do that... */ +/* If you are writing a driver, please use dev_dbg instead */ +#if defined(DEBUG) +#define pr_debug_ratelimited(fmt, ...) \ + printk_ratelimited(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__) +#else +#define pr_debug_ratelimited(fmt, ...) \ + ({ if (0) printk_ratelimited(KERN_DEBUG pr_fmt(fmt), \ + ##__VA_ARGS__); 0; }) +#endif + /* * General tracing related utility functions - trace_printk(), * tracing_on/tracing_off and tracing_start()/tracing_stop -- 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