diff options
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/ftrace.txt | 87 | ||||
| -rw-r--r-- | Documentation/markers.txt | 15 | ||||
| -rw-r--r-- | Documentation/tracepoints.txt | 4 |
3 files changed, 97 insertions, 9 deletions
diff --git a/Documentation/ftrace.txt b/Documentation/ftrace.txt index 35a78bc..803b131 100644 --- a/Documentation/ftrace.txt +++ b/Documentation/ftrace.txt @@ -127,6 +127,8 @@ of ftrace. Here is a list of some of the key files: be traced. If a function exists in both set_ftrace_filter and set_ftrace_notrace, the function will _not_ be traced. + set_ftrace_pid: Have the function tracer only trace a single thread. + available_filter_functions: This lists the functions that ftrace has processed and can trace. These are the function names that you can pass to "set_ftrace_filter" or @@ -1073,6 +1075,83 @@ For simple one time traces, the above is sufficent. For anything else, a search through /proc/mounts may be needed to find where the debugfs file-system is mounted. + +Single thread tracing +--------------------- + +By writing into /debug/tracing/set_ftrace_pid you can trace a +single thread. For example: + +# cat /debug/tracing/set_ftrace_pid +no pid +# echo 3111 > /debug/tracing/set_ftrace_pid +# cat /debug/tracing/set_ftrace_pid +3111 +# echo function > /debug/tracing/current_tracer +# cat /debug/tracing/trace | head + # tracer: function + # + # TASK-PID CPU# TIMESTAMP FUNCTION + # | | | | | + yum-updatesd-3111 [003] 1637.254676: finish_task_switch <-thread_return + yum-updatesd-3111 [003] 1637.254681: hrtimer_cancel <-schedule_hrtimeout_range + yum-updatesd-3111 [003] 1637.254682: hrtimer_try_to_cancel <-hrtimer_cancel + yum-updatesd-3111 [003] 1637.254683: lock_hrtimer_base <-hrtimer_try_to_cancel + yum-updatesd-3111 [003] 1637.254685: fget_light <-do_sys_poll + yum-updatesd-3111 [003] 1637.254686: pipe_poll <-do_sys_poll +# echo -1 > /debug/tracing/set_ftrace_pid +# cat /debug/tracing/trace |head + # tracer: function + # + # TASK-PID CPU# TIMESTAMP FUNCTION + # | | | | | + ##### CPU 3 buffer started #### + yum-updatesd-3111 [003] 1701.957688: free_poll_entry <-poll_freewait + yum-updatesd-3111 [003] 1701.957689: remove_wait_queue <-free_poll_entry + yum-updatesd-3111 [003] 1701.957691: fput <-free_poll_entry + yum-updatesd-3111 [003] 1701.957692: audit_syscall_exit <-sysret_audit + yum-updatesd-3111 [003] 1701.957693: path_put <-audit_syscall_exit + +If you want to trace a function when executing, you could use +something like this simple program: + +#include <stdio.h> +#include <stdlib.h> +#include <sys/types.h> +#include <sys/stat.h> +#include <fcntl.h> +#include <unistd.h> + +int main (int argc, char **argv) +{ + if (argc < 1) + exit(-1); + + if (fork() > 0) { + int fd, ffd; + char line[64]; + int s; + + ffd = open("/debug/tracing/current_tracer", O_WRONLY); + if (ffd < 0) + exit(-1); + write(ffd, "nop", 3); + + fd = open("/debug/tracing/set_ftrace_pid", O_WRONLY); + s = sprintf(line, "%d\n", getpid()); + write(fd, line, s); + + write(ffd, "function", 8); + + close(fd); + close(ffd); + + execvp(argv[1], argv+1); + } + + return 0; +} + dynamic ftrace -------------- @@ -1172,7 +1251,11 @@ These are the only wild cards which are supported. <match>*<match> will not work. - # echo hrtimer_* > /debug/tracing/set_ftrace_filter +Note: It is better to use quotes to enclose the wild cards, otherwise + the shell may expand the parameters into names of files in the local + directory. + + # echo 'hrtimer_*' > /debug/tracing/set_ftrace_filter Produces: @@ -1227,7 +1310,7 @@ Again, now we want to append. # echo sys_nanosleep > /debug/tracing/set_ftrace_filter # cat /debug/tracing/set_ftrace_filter sys_nanosleep - # echo hrtimer_* >> /debug/tracing/set_ftrace_filter + # echo 'hrtimer_*' >> /debug/tracing/set_ftrace_filter # cat /debug/tracing/set_ftrace_filter hrtimer_run_queues hrtimer_run_pending diff --git a/Documentation/markers.txt b/Documentation/markers.txt index 6d275e4..d2b3d0e 100644 --- a/Documentation/markers.txt +++ b/Documentation/markers.txt @@ -51,11 +51,16 @@ to call) for the specific marker through marker_probe_register() and can be activated by calling marker_arm(). Marker deactivation can be done by calling marker_disarm() as many times as marker_arm() has been called. Removing a probe is done through marker_probe_unregister(); it will disarm the probe. -marker_synchronize_unregister() must be called before the end of the module exit -function to make sure there is no caller left using the probe. This, and the -fact that preemption is disabled around the probe call, make sure that probe -removal and module unload are safe. See the "Probe example" section below for a -sample probe module. + +marker_synchronize_unregister() must be called between probe unregistration and +the first occurrence of +- the end of module exit function, + to make sure there is no caller left using the probe; +- the free of any resource used by the probes, + to make sure the probes wont be accessing invalid data. +This, and the fact that preemption is disabled around the probe call, make sure +that probe removal and module unload are safe. See the "Probe example" section +below for a sample probe module. The marker mechanism supports inserting multiple instances of the same marker. Markers can be put in inline functions, inlined static functions, and diff --git a/Documentation/tracepoints.txt b/Documentation/tracepoints.txt index 2d42241..6f0a044 100644 --- a/Documentation/tracepoints.txt +++ b/Documentation/tracepoints.txt @@ -45,7 +45,7 @@ In include/trace/subsys.h : #include <linux/tracepoint.h> DECLARE_TRACE(subsys_eventname, - TPPTOTO(int firstarg, struct task_struct *p), + TPPROTO(int firstarg, struct task_struct *p), TPARGS(firstarg, p)); In subsys/file.c (where the tracing statement must be added) : @@ -66,7 +66,7 @@ Where : - subsys is the name of your subsystem. - eventname is the name of the event to trace. -- TPPTOTO(int firstarg, struct task_struct *p) is the prototype of the +- TPPROTO(int firstarg, struct task_struct *p) is the prototype of the function called by this tracepoint. - TPARGS(firstarg, p) are the parameters names, same as found in the |