From: Masami Hiramatsu <masami.hiramatsu...@hitachi.com> Modify soft-mode flag only if no other soft-mode referrer (currently only the ftrace triggers) by using a reference counter in each ftrace_event_file.
Without this fix, adding and removing several different enable/disable_event triggers on the same event clear soft-mode bit from the ftrace_event_file. This also happens with a typo of glob on setting triggers. e.g. # echo vfs_symlink:enable_event:net:netif_rx > set_ftrace_filter # cat events/net/netif_rx/enable 0* # echo typo_func:enable_event:net:netif_rx > set_ftrace_filter # cat events/net/netif_rx/enable 0 # cat set_ftrace_filter #### all functions enabled #### vfs_symlink:enable_event:net:netif_rx:unlimited As above, we still have a trigger, but soft-mode is gone. Link: http://lkml.kernel.org/r/20130509054429.30398.7464.stgit@mhiramat-M0-7522 Cc: Srikar Dronamraju <sri...@linux.vnet.ibm.com> Cc: Oleg Nesterov <o...@redhat.com> Cc: Frederic Weisbecker <fweis...@gmail.com> Cc: Ingo Molnar <mi...@redhat.com> Cc: David Sharp <dhsh...@google.com> Cc: Hiraku Toyooka <hiraku.toyooka...@hitachi.com> Cc: Tom Zanussi <tom.zanu...@intel.com> Signed-off-by: Masami Hiramatsu <masami.hiramatsu...@hitachi.com> Signed-off-by: Steven Rostedt <rost...@goodmis.org> --- include/linux/ftrace_event.h | 1 + kernel/trace/trace_events.c | 12 ++++++++++-- 2 files changed, 11 insertions(+), 2 deletions(-) diff --git a/include/linux/ftrace_event.h b/include/linux/ftrace_event.h index 34e00fb..4372658 100644 --- a/include/linux/ftrace_event.h +++ b/include/linux/ftrace_event.h @@ -293,6 +293,7 @@ struct ftrace_event_file { * caching and such. Which is mostly OK ;-) */ unsigned long flags; + atomic_t sm_ref; /* soft-mode reference counter */ }; #define __TRACE_EVENT_FLAGS(name, value) \ diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c index 915c136..8be1224 100644 --- a/kernel/trace/trace_events.c +++ b/kernel/trace/trace_events.c @@ -251,7 +251,8 @@ static int __ftrace_event_enable_disable(struct ftrace_event_file *file, switch (enable) { case 0: /* - * When soft_disable is set and enable is cleared, we want + * When soft_disable is set and enable is cleared, the sm_ref + * reference counter is decremented. If it reaches 0, we want * to clear the SOFT_DISABLED flag but leave the event in the * state that it was. That is, if the event was enabled and * SOFT_DISABLED isn't set, then do nothing. But if SOFT_DISABLED @@ -263,6 +264,8 @@ static int __ftrace_event_enable_disable(struct ftrace_event_file *file, * "soft enable"s (clearing the SOFT_DISABLED bit) wont work. */ if (soft_disable) { + if (atomic_dec_return(&file->sm_ref) > 0) + break; disable = file->flags & FTRACE_EVENT_FL_SOFT_DISABLED; clear_bit(FTRACE_EVENT_FL_SOFT_MODE_BIT, &file->flags); } else @@ -291,8 +294,11 @@ static int __ftrace_event_enable_disable(struct ftrace_event_file *file, */ if (!soft_disable) clear_bit(FTRACE_EVENT_FL_SOFT_DISABLED_BIT, &file->flags); - else + else { + if (atomic_inc_return(&file->sm_ref) > 1) + break; set_bit(FTRACE_EVENT_FL_SOFT_MODE_BIT, &file->flags); + } if (!(file->flags & FTRACE_EVENT_FL_ENABLED)) { @@ -1540,6 +1546,7 @@ __trace_add_new_event(struct ftrace_event_call *call, file->event_call = call; file->tr = tr; + atomic_set(&file->sm_ref, 0); list_add(&file->list, &tr->events); return event_create_dir(tr->event_dir, file, id, enable, filter, format); @@ -1562,6 +1569,7 @@ __trace_early_add_new_event(struct ftrace_event_call *call, file->event_call = call; file->tr = tr; + atomic_set(&file->sm_ref, 0); list_add(&file->list, &tr->events); return 0; -- 1.7.10.4
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