tracing: Modify soft-mode only if there's no other referrer
authorMasami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Thu, 9 May 2013 05:44:29 +0000 (14:44 +0900)
committerSteven Rostedt <rostedt@goodmis.org>
Fri, 10 May 2013 00:14:25 +0000 (20:14 -0400)
commit1cf4c0732db3cd3c49cadbc60ff6bda08604e6fa
tree74133737a3ecea18847788c10fae7bb474f1aaa8
parent30052170dcc256c18a43fb3e76577a67394543f8
tracing: Modify soft-mode only if there's no other referrer

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 <srikar@linux.vnet.ibm.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: David Sharp <dhsharp@google.com>
Cc: Hiraku Toyooka <hiraku.toyooka.gu@hitachi.com>
Cc: Tom Zanussi <tom.zanussi@intel.com>
Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
include/linux/ftrace_event.h
kernel/trace/trace_events.c