diff options
Diffstat (limited to 'Documentation/trace')
-rw-r--r-- | Documentation/trace/events.txt | 11 | ||||
-rw-r--r-- | Documentation/trace/ftrace.txt | 52 | ||||
-rw-r--r-- | Documentation/trace/kprobetrace.txt | 4 |
3 files changed, 58 insertions, 9 deletions
diff --git a/Documentation/trace/events.txt b/Documentation/trace/events.txt index 02ac6ed38b2d..09bd8e902989 100644 --- a/Documentation/trace/events.txt +++ b/Documentation/trace/events.txt @@ -90,7 +90,8 @@ In order to facilitate early boot debugging, use boot option: trace_event=[event-list] -The format of this boot option is the same as described in section 2.1. +event-list is a comma separated list of events. See section 2.1 for event +format. 3. Defining an event-enabled tracepoint ======================================= @@ -238,7 +239,7 @@ subsystem's filter file. For convenience, filters for every event in a subsystem can be set or cleared as a group by writing a filter expression into the filter file -at the root of the subsytem. Note however, that if a filter for any +at the root of the subsystem. Note however, that if a filter for any event within the subsystem lacks a field specified in the subsystem filter, or if the filter can't be applied for any other reason, the filter for that event will retain its previous setting. This can @@ -250,7 +251,7 @@ fields can be guaranteed to propagate successfully to all events. Here are a few subsystem filter examples that also illustrate the above points: -Clear the filters on all events in the sched subsytem: +Clear the filters on all events in the sched subsystem: # cd /sys/kernel/debug/tracing/events/sched # echo 0 > filter @@ -260,7 +261,7 @@ none none Set a filter using only common fields for all events in the sched -subsytem (all events end up with the same filter): +subsystem (all events end up with the same filter): # cd /sys/kernel/debug/tracing/events/sched # echo common_pid == 0 > filter @@ -270,7 +271,7 @@ common_pid == 0 common_pid == 0 Attempt to set a filter using a non-common field for all events in the -sched subsytem (all events but those that have a prev_pid field retain +sched subsystem (all events but those that have a prev_pid field retain their old filters): # cd /sys/kernel/debug/tracing/events/sched diff --git a/Documentation/trace/ftrace.txt b/Documentation/trace/ftrace.txt index bab3040da548..557c1edeccaf 100644 --- a/Documentation/trace/ftrace.txt +++ b/Documentation/trace/ftrace.txt @@ -155,6 +155,9 @@ of ftrace. Here is a list of some of the key files: to be traced. Echoing names of functions into this file will limit the trace to only those functions. + This interface also allows for commands to be used. See the + "Filter commands" section for more details. + set_ftrace_notrace: This has an effect opposite to that of @@ -1337,12 +1340,14 @@ ftrace_dump_on_oops must be set. To set ftrace_dump_on_oops, one can either use the sysctl function or set it via the proc system interface. - sysctl kernel.ftrace_dump_on_oops=1 + sysctl kernel.ftrace_dump_on_oops=n or - echo 1 > /proc/sys/kernel/ftrace_dump_on_oops + echo n > /proc/sys/kernel/ftrace_dump_on_oops +If n = 1, ftrace will dump buffers of all CPUs, if n = 2 ftrace will +only dump the buffer of the CPU that triggered the oops. Here's an example of such a dump after a null pointer dereference in a kernel module: @@ -1588,7 +1593,7 @@ module author does not need to worry about it. When tracing is enabled, kstop_machine is called to prevent races with the CPUS executing code being modified (which can -cause the CPU to do undesireable things), and the nops are +cause the CPU to do undesirable things), and the nops are patched back to calls. But this time, they do not call mcount (which is just a function stub). They now call into the ftrace infrastructure. @@ -1822,6 +1827,47 @@ this special filter via: echo > set_graph_function +Filter commands +--------------- + +A few commands are supported by the set_ftrace_filter interface. +Trace commands have the following format: + +<function>:<command>:<parameter> + +The following commands are supported: + +- mod + This command enables function filtering per module. The + parameter defines the module. For example, if only the write* + functions in the ext3 module are desired, run: + + echo 'write*:mod:ext3' > set_ftrace_filter + + This command interacts with the filter in the same way as + filtering based on function names. Thus, adding more functions + in a different module is accomplished by appending (>>) to the + filter file. Remove specific module functions by prepending + '!': + + echo '!writeback*:mod:ext3' >> set_ftrace_filter + +- traceon/traceoff + These commands turn tracing on and off when the specified + functions are hit. The parameter determines how many times the + tracing system is turned on and off. If unspecified, there is + no limit. For example, to disable tracing when a schedule bug + is hit the first 5 times, run: + + echo '__schedule_bug:traceoff:5' > set_ftrace_filter + + These commands are cumulative whether or not they are appended + to set_ftrace_filter. To remove a command, prepend it by '!' + and drop the parameter: + + echo '!__schedule_bug:traceoff' > set_ftrace_filter + + trace_pipe ---------- diff --git a/Documentation/trace/kprobetrace.txt b/Documentation/trace/kprobetrace.txt index a9100b28eb84..ec94748ae65b 100644 --- a/Documentation/trace/kprobetrace.txt +++ b/Documentation/trace/kprobetrace.txt @@ -40,7 +40,9 @@ Synopsis of kprobe_events $stack : Fetch stack address. $retval : Fetch return value.(*) +|-offs(FETCHARG) : Fetch memory at FETCHARG +|- offs address.(**) - NAME=FETCHARG: Set NAME as the argument name of FETCHARG. + NAME=FETCHARG : Set NAME as the argument name of FETCHARG. + FETCHARG:TYPE : Set TYPE as the type of FETCHARG. Currently, basic types + (u8/u16/u32/u64/s8/s16/s32/s64) are supported. (*) only for return probe. (**) this is useful for fetching a field of data structures. |