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 --- kernel/trace/trace.c | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) (limited to 'kernel/trace/trace.c') diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 88bd9ae2a9ed..f531301b7a3b 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -1151,6 +1151,22 @@ void __trace_stack(struct trace_array *tr, unsigned long flags, int skip, __ftrace_trace_stack(tr->buffer, flags, skip, pc); } +/** + * trace_dump_stack - record a stack back trace in the trace buffer + */ +void trace_dump_stack(void) +{ + unsigned long flags; + + if (tracing_disabled || tracing_selftest_running) + return 0; + + local_save_flags(flags); + + /* skipping 3 traces, seems to get us at the caller of this function */ + __ftrace_trace_stack(global_trace.buffer, flags, 3, preempt_count()); +} + void ftrace_trace_userstack(struct ring_buffer *buffer, unsigned long flags, int pc) { -- cgit v1.2.3 From fdb372ed4cadbfe9dbba0e932a77d0523682e690 Mon Sep 17 00:00:00 2001 From: Li Zefan Date: Tue, 8 Dec 2009 11:15:59 +0800 Subject: tracing: Use seq file for trace_options Code simplification for reading trace_options. Signed-off-by: Li Zefan Acked-by: Steven Rostedt LKML-reference: <4B1DC4EF.3090106@cn.fujitsu.com> Signed-off-by: Frederic Weisbecker --- kernel/trace/trace.c | 60 +++++++++++++++------------------------------------- 1 file changed, 17 insertions(+), 43 deletions(-) (limited to 'kernel/trace/trace.c') diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 88bd9ae2a9ed..a6c41cc63285 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -2316,67 +2316,32 @@ static const struct file_operations tracing_cpumask_fops = { .write = tracing_cpumask_write, }; -static ssize_t -tracing_trace_options_read(struct file *filp, char __user *ubuf, - size_t cnt, loff_t *ppos) +static int tracing_trace_options_show(struct seq_file *m, void *v) { struct tracer_opt *trace_opts; u32 tracer_flags; - int len = 0; - char *buf; - int r = 0; int i; - - /* calculate max size */ - for (i = 0; trace_options[i]; i++) { - len += strlen(trace_options[i]); - len += 3; /* "no" and newline */ - } - mutex_lock(&trace_types_lock); tracer_flags = current_trace->flags->val; trace_opts = current_trace->flags->opts; - /* - * Increase the size with names of options specific - * of the current tracer. - */ - for (i = 0; trace_opts[i].name; i++) { - len += strlen(trace_opts[i].name); - len += 3; /* "no" and newline */ - } - - /* +1 for \0 */ - buf = kmalloc(len + 1, GFP_KERNEL); - if (!buf) { - mutex_unlock(&trace_types_lock); - return -ENOMEM; - } - for (i = 0; trace_options[i]; i++) { if (trace_flags & (1 << i)) - r += sprintf(buf + r, "%s\n", trace_options[i]); + seq_printf(m, "%s\n", trace_options[i]); else - r += sprintf(buf + r, "no%s\n", trace_options[i]); + seq_printf(m, "no%s\n", trace_options[i]); } for (i = 0; trace_opts[i].name; i++) { if (tracer_flags & trace_opts[i].bit) - r += sprintf(buf + r, "%s\n", - trace_opts[i].name); + seq_printf(m, "%s\n", trace_opts[i].name); else - r += sprintf(buf + r, "no%s\n", - trace_opts[i].name); + seq_printf(m, "no%s\n", trace_opts[i].name); } mutex_unlock(&trace_types_lock); - WARN_ON(r >= len + 1); - - r = simple_read_from_buffer(ubuf, cnt, ppos, buf, r); - - kfree(buf); - return r; + return 0; } /* Try to assign a tracer specific option */ @@ -2471,9 +2436,18 @@ tracing_trace_options_write(struct file *filp, const char __user *ubuf, return cnt; } +static int tracing_trace_options_open(struct inode *inode, struct file *file) +{ + if (tracing_disabled) + return -ENODEV; + return single_open(file, tracing_trace_options_show, NULL); +} + static const struct file_operations tracing_iter_fops = { - .open = tracing_open_generic, - .read = tracing_trace_options_read, + .open = tracing_trace_options_open, + .read = seq_read, + .llseek = seq_lseek, + .release = single_release, .write = tracing_trace_options_write, }; -- cgit v1.2.3 From 13f16d209161c95e92aef40e350cc6cf56ac440b Mon Sep 17 00:00:00 2001 From: Li Zefan Date: Tue, 8 Dec 2009 11:16:11 +0800 Subject: tracing: Use seq file for trace_clock The buffer for the output is as small as 64 bytes, so it'll overflow if we add more clock type. Use seq file instead. Signed-off-by: Li Zefan Acked-by: Steven Rostedt LKML-Reference: <4B1DC4FB.5030407@cn.fujitsu.com> Signed-off-by: Frederic Weisbecker --- kernel/trace/trace.c | 24 +++++++++++++++--------- 1 file changed, 15 insertions(+), 9 deletions(-) (limited to 'kernel/trace/trace.c') diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index a6c41cc63285..886268e0d8ee 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -3366,21 +3366,18 @@ tracing_mark_write(struct file *filp, const char __user *ubuf, return cnt; } -static ssize_t tracing_clock_read(struct file *filp, char __user *ubuf, - size_t cnt, loff_t *ppos) +static int tracing_clock_show(struct seq_file *m, void *v) { - char buf[64]; - int bufiter = 0; int i; for (i = 0; i < ARRAY_SIZE(trace_clocks); i++) - bufiter += snprintf(buf + bufiter, sizeof(buf) - bufiter, + seq_printf(m, "%s%s%s%s", i ? " " : "", i == trace_clock_id ? "[" : "", trace_clocks[i].name, i == trace_clock_id ? "]" : ""); - bufiter += snprintf(buf + bufiter, sizeof(buf) - bufiter, "\n"); + seq_putc(m, '\n'); - return simple_read_from_buffer(ubuf, cnt, ppos, buf, bufiter); + return 0; } static ssize_t tracing_clock_write(struct file *filp, const char __user *ubuf, @@ -3422,6 +3419,13 @@ static ssize_t tracing_clock_write(struct file *filp, const char __user *ubuf, return cnt; } +static int tracing_clock_open(struct inode *inode, struct file *file) +{ + if (tracing_disabled) + return -ENODEV; + return single_open(file, tracing_clock_show, NULL); +} + static const struct file_operations tracing_max_lat_fops = { .open = tracing_open_generic, .read = tracing_max_lat_read, @@ -3460,8 +3464,10 @@ static const struct file_operations tracing_mark_fops = { }; static const struct file_operations trace_clock_fops = { - .open = tracing_open_generic, - .read = tracing_clock_read, + .open = tracing_clock_open, + .read = seq_read, + .llseek = seq_lseek, + .release = single_release, .write = tracing_clock_write, }; -- cgit v1.2.3 From 2cbafd68b826f8e0471875cf33cdfb8a1478aef1 Mon Sep 17 00:00:00 2001 From: Li Zefan Date: Tue, 8 Dec 2009 11:16:26 +0800 Subject: tracing: Remove useless trace option Since commit 4d9493c90f8e6e1b164aede3814010a290161abb ("ftrace: remove add-hoc code"), option "sched-tree" has become useless. Signed-off-by: Li Zefan Acked-by: Steven Rostedt LKML-Reference: <4B1DC50A.7040402@cn.fujitsu.com> Signed-off-by: Frederic Weisbecker --- kernel/trace/trace.c | 1 - kernel/trace/trace.h | 23 +++++++++++------------ 2 files changed, 11 insertions(+), 13 deletions(-) (limited to 'kernel/trace/trace.c') diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 886268e0d8ee..898409d60422 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -313,7 +313,6 @@ static const char *trace_options[] = { "bin", "block", "stacktrace", - "sched-tree", "trace_printk", "ftrace_preempt", "branch", diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h index 7fa33cab6962..1b18cb240c16 100644 --- a/kernel/trace/trace.h +++ b/kernel/trace/trace.h @@ -597,18 +597,17 @@ enum trace_iterator_flags { TRACE_ITER_BIN = 0x40, TRACE_ITER_BLOCK = 0x80, TRACE_ITER_STACKTRACE = 0x100, - TRACE_ITER_SCHED_TREE = 0x200, - TRACE_ITER_PRINTK = 0x400, - TRACE_ITER_PREEMPTONLY = 0x800, - TRACE_ITER_BRANCH = 0x1000, - TRACE_ITER_ANNOTATE = 0x2000, - TRACE_ITER_USERSTACKTRACE = 0x4000, - TRACE_ITER_SYM_USEROBJ = 0x8000, - TRACE_ITER_PRINTK_MSGONLY = 0x10000, - TRACE_ITER_CONTEXT_INFO = 0x20000, /* Print pid/cpu/time */ - TRACE_ITER_LATENCY_FMT = 0x40000, - TRACE_ITER_SLEEP_TIME = 0x80000, - TRACE_ITER_GRAPH_TIME = 0x100000, + TRACE_ITER_PRINTK = 0x200, + TRACE_ITER_PREEMPTONLY = 0x400, + TRACE_ITER_BRANCH = 0x800, + TRACE_ITER_ANNOTATE = 0x1000, + TRACE_ITER_USERSTACKTRACE = 0x2000, + TRACE_ITER_SYM_USEROBJ = 0x4000, + TRACE_ITER_PRINTK_MSGONLY = 0x8000, + TRACE_ITER_CONTEXT_INFO = 0x10000, /* Print pid/cpu/time */ + TRACE_ITER_LATENCY_FMT = 0x20000, + TRACE_ITER_SLEEP_TIME = 0x40000, + TRACE_ITER_GRAPH_TIME = 0x80000, }; /* -- cgit v1.2.3 From 8d18eaaff5acaa58369be342c86e607643ce10c7 Mon Sep 17 00:00:00 2001 From: Li Zefan Date: Tue, 8 Dec 2009 11:17:06 +0800 Subject: tracing: Simplify trace_option_write() - remove duplicate code inside trace_options_write() - extract duplicate code in trace_options_write() and set_tracer_option() Signed-off-by: Li Zefan Acked-by: Steven Rostedt LKML-Reference: <4B1DC532.9010802@cn.fujitsu.com> Signed-off-by: Frederic Weisbecker --- kernel/trace/trace.c | 85 +++++++++++++++++++--------------------------------- 1 file changed, 31 insertions(+), 54 deletions(-) (limited to 'kernel/trace/trace.c') diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 898409d60422..05076008f371 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -2343,38 +2343,39 @@ static int tracing_trace_options_show(struct seq_file *m, void *v) return 0; } +static int __set_tracer_option(struct tracer *trace, + struct tracer_flags *tracer_flags, + struct tracer_opt *opts, int neg) +{ + int ret; + + ret = trace->set_flag(tracer_flags->val, opts->bit, !neg); + if (ret) + return ret; + + if (neg) + tracer_flags->val &= ~opts->bit; + else + tracer_flags->val |= opts->bit; + return 0; +} + /* Try to assign a tracer specific option */ static int set_tracer_option(struct tracer *trace, char *cmp, int neg) { struct tracer_flags *tracer_flags = trace->flags; struct tracer_opt *opts = NULL; - int ret = 0, i = 0; - int len; + int i; for (i = 0; tracer_flags->opts[i].name; i++) { opts = &tracer_flags->opts[i]; - len = strlen(opts->name); - if (strncmp(cmp, opts->name, len) == 0) { - ret = trace->set_flag(tracer_flags->val, - opts->bit, !neg); - break; - } + if (strcmp(cmp, opts->name) == 0) + return __set_tracer_option(trace, trace->flags, + opts, neg); } - /* Not found */ - if (!tracer_flags->opts[i].name) - return -EINVAL; - /* Refused to handle */ - if (ret) - return ret; - - if (neg) - tracer_flags->val &= ~opts->bit; - else - tracer_flags->val |= opts->bit; - - return 0; + return -EINVAL; } static void set_tracer_flags(unsigned int mask, int enabled) @@ -2394,7 +2395,7 @@ tracing_trace_options_write(struct file *filp, const char __user *ubuf, size_t cnt, loff_t *ppos) { char buf[64]; - char *cmp = buf; + char *cmp; int neg = 0; int ret; int i; @@ -2406,16 +2407,15 @@ tracing_trace_options_write(struct file *filp, const char __user *ubuf, return -EFAULT; buf[cnt] = 0; + cmp = strstrip(buf); - if (strncmp(buf, "no", 2) == 0) { + if (strncmp(cmp, "no", 2) == 0) { neg = 1; cmp += 2; } for (i = 0; trace_options[i]; i++) { - int len = strlen(trace_options[i]); - - if (strncmp(cmp, trace_options[i], len) == 0) { + if (strcmp(cmp, trace_options[i]) == 0) { set_tracer_flags(1 << i, !neg); break; } @@ -3927,39 +3927,16 @@ trace_options_write(struct file *filp, const char __user *ubuf, size_t cnt, if (ret < 0) return ret; - ret = 0; - switch (val) { - case 0: - /* do nothing if already cleared */ - if (!(topt->flags->val & topt->opt->bit)) - break; - - mutex_lock(&trace_types_lock); - if (current_trace->set_flag) - ret = current_trace->set_flag(topt->flags->val, - topt->opt->bit, 0); - mutex_unlock(&trace_types_lock); - if (ret) - return ret; - topt->flags->val &= ~topt->opt->bit; - break; - case 1: - /* do nothing if already set */ - if (topt->flags->val & topt->opt->bit) - break; + if (val != 0 && val != 1) + return -EINVAL; + if (!!(topt->flags->val & topt->opt->bit) != val) { mutex_lock(&trace_types_lock); - if (current_trace->set_flag) - ret = current_trace->set_flag(topt->flags->val, - topt->opt->bit, 1); + ret = __set_tracer_option(current_trace, topt->flags, + topt->opt, val); mutex_unlock(&trace_types_lock); if (ret) return ret; - topt->flags->val |= topt->opt->bit; - break; - - default: - return -EINVAL; } *ppos += cnt; -- 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 'kernel/trace/trace.c') 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