From c85a17e22695969aa24a7ffa40cf26d6e6fcfd50 Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Sat, 20 Jun 2009 05:45:14 +0200 Subject: tracing/urgent: fix unbalanced ftrace_start_up Perfcounter reports the following stats for a wide system profiling: # # (2364 samples) # # Overhead Symbol # ........ ...... # 15.40% [k] mwait_idle_with_hints 8.29% [k] read_hpet 5.75% [k] ftrace_caller 3.60% [k] ftrace_call [...] This snapshot has been taken while neither the function tracer nor the function graph tracer was running. With dynamic ftrace, such results show a wrong ftrace behaviour because all calls to ftrace_caller or ftrace_graph_caller (the patched calls to mcount) are supposed to be patched into nop if none of those tracers are running. The problem occurs after the first run of the function tracer. Once we launch it a second time, the callsites will never be nopped back, unless you set custom filters. For example it happens during the self tests at boot time. The function tracer selftest runs, and then the dynamic tracing is tested too. After that, the callsites are left un-nopped. This is because the reset callback of the function tracer tries to unregister two ftrace callbacks in once: the common function tracer and the function tracer with stack backtrace, regardless of which one is currently in use. It then creates an unbalance on ftrace_start_up value which is expected to be zero when the last ftrace callback is unregistered. When it reaches zero, the FTRACE_DISABLE_CALLS is set on the next ftrace command, triggering the patching into nop. But since it becomes unbalanced, ie becomes lower than zero, if the kernel functions are patched again (as in every further function tracer runs), they won't ever be nopped back. Note that ftrace_call and ftrace_graph_call are still patched back to ftrace_stub in the off case, but not the callers of ftrace_call and ftrace_graph_caller. It means that the tracing is well deactivated but we waste a useless call into every kernel function. This patch just unregisters the right ftrace_ops for the function tracer on its reset callback and ignores the other one which is not registered, fixing the unbalance. The problem also happens is .30 Signed-off-by: Frederic Weisbecker Cc: Steven Rostedt Cc: stable@kernel.org --- kernel/trace/trace_functions.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) (limited to 'kernel/trace/trace_functions.c') diff --git a/kernel/trace/trace_functions.c b/kernel/trace/trace_functions.c index c9a0b7df44ff..90f134764837 100644 --- a/kernel/trace/trace_functions.c +++ b/kernel/trace/trace_functions.c @@ -193,9 +193,11 @@ static void tracing_start_function_trace(void) static void tracing_stop_function_trace(void) { ftrace_function_enabled = 0; - /* OK if they are not registered */ - unregister_ftrace_function(&trace_stack_ops); - unregister_ftrace_function(&trace_ops); + + if (func_flags.val & TRACE_FUNC_OPT_STACK) + unregister_ftrace_function(&trace_stack_ops); + else + unregister_ftrace_function(&trace_ops); } static int func_set_flag(u32 old_flags, u32 bit, int set) -- cgit v1.2.3 From 00e54d087afb3867b0b461aef6c1ff433d0df564 Mon Sep 17 00:00:00 2001 From: Li Zefan Date: Thu, 25 Jun 2009 14:05:27 +0800 Subject: ftrace: Remove duplicate newline Before: # echo 'sys_open:traceon:' > set_ftrace_filter # echo 'sys_close:traceoff:5' > set_ftrace_filter # cat set_ftrace_filter #### all functions enabled #### sys_open:traceon:unlimited sys_close:traceoff:count=0 After: # cat set_ftrace_filter #### all functions enabled #### sys_open:traceon:unlimited sys_close:traceoff:count=0 Signed-off-by: Li Zefan Cc: Steven Rostedt Cc: Frederic Weisbecker LKML-Reference: <4A4313A7.7030105@cn.fujitsu.com> Signed-off-by: Ingo Molnar --- kernel/trace/trace_functions.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) (limited to 'kernel/trace/trace_functions.c') diff --git a/kernel/trace/trace_functions.c b/kernel/trace/trace_functions.c index 90f134764837..7402144bff21 100644 --- a/kernel/trace/trace_functions.c +++ b/kernel/trace/trace_functions.c @@ -302,8 +302,7 @@ ftrace_trace_onoff_print(struct seq_file *m, unsigned long ip, if (count == -1) seq_printf(m, ":unlimited\n"); else - seq_printf(m, ":count=%ld", count); - seq_putc(m, '\n'); + seq_printf(m, ":count=%ld\n", count); return 0; } -- cgit v1.2.3 From 04aef32d39cc4ef80087c0ce8ed113c6d64f1a6b Mon Sep 17 00:00:00 2001 From: Xiao Guangrong Date: Wed, 15 Jul 2009 12:29:06 +0800 Subject: tracing/function: Fix the return value of ftrace_trace_onoff_callback() ftrace_trace_onoff_callback() will return an error even if we do the right operation, for example: # echo _spin_*:traceon:10 > set_ftrace_filter -bash: echo: write error: Invalid argument # cat set_ftrace_filter #### all functions enabled #### _spin_trylock_bh:traceon:count=10 _spin_unlock_irq:traceon:count=10 _spin_unlock_bh:traceon:count=10 _spin_lock_irq:traceon:count=10 _spin_unlock:traceon:count=10 _spin_trylock:traceon:count=10 _spin_unlock_irqrestore:traceon:count=10 _spin_lock_irqsave:traceon:count=10 _spin_lock_bh:traceon:count=10 _spin_lock:traceon:count=10 We want to set _spin_*:traceon:10 to set_ftrace_filter, it complains with "Invalid argument", but the operation is successful. This is because ftrace_process_regex() returns the number of functions that matched the pattern. If the number is not 0, this value is returned by ftrace_regex_write() whereas we want to return the number of bytes virtually written. Also the file offset pointer is not updated in this case. If the number of matched functions is lower than the number of bytes written by the user, this results to a reprocessing of the string given by the user with a lower size, leading to a malformed ftrace regex and then a -EINVAL returned. So, this patch fixes it by returning 0 if no error occured. The fix also applies on 2.6.30 Signed-off-by: Xiao Guangrong Reviewed-by: Li Zefan Cc: stable@kernel.org Signed-off-by: Frederic Weisbecker --- kernel/trace/trace_functions.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'kernel/trace/trace_functions.c') diff --git a/kernel/trace/trace_functions.c b/kernel/trace/trace_functions.c index 7402144bff21..75ef000613c3 100644 --- a/kernel/trace/trace_functions.c +++ b/kernel/trace/trace_functions.c @@ -363,7 +363,7 @@ ftrace_trace_onoff_callback(char *glob, char *cmd, char *param, int enable) out_reg: ret = register_ftrace_function_probe(glob, ops, count); - return ret; + return ret < 0 ? ret : 0; } static struct ftrace_func_command ftrace_traceon_cmd = { -- cgit v1.2.3 From 6f2f3cf00ee32f75ba007a46bab88a54d68a5deb Mon Sep 17 00:00:00 2001 From: Xiao Guangrong Date: Thu, 16 Jul 2009 14:21:08 +0800 Subject: tracing/function: Cleanup for function tracer We can directly use %pf input format instead of kallsyms_lookup() and %s input format Signed-off-by: Xiao Guangrong Reviewed-by: Li Zefan Signed-off-by: Frederic Weisbecker --- kernel/trace/trace_functions.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-) (limited to 'kernel/trace/trace_functions.c') diff --git a/kernel/trace/trace_functions.c b/kernel/trace/trace_functions.c index 7402144bff21..b53dc994dfb6 100644 --- a/kernel/trace/trace_functions.c +++ b/kernel/trace/trace_functions.c @@ -288,11 +288,9 @@ static int ftrace_trace_onoff_print(struct seq_file *m, unsigned long ip, struct ftrace_probe_ops *ops, void *data) { - char str[KSYM_SYMBOL_LEN]; long count = (long)data; - kallsyms_lookup(ip, NULL, NULL, NULL, str); - seq_printf(m, "%s:", str); + seq_printf(m, "%pf:", (void *)ip); if (ops == &traceon_probe_ops) seq_printf(m, "traceon"); -- cgit v1.2.3