tracing/filters: fix race between filter setting and module unload
Module unload is protected by event_mutex, while setting filter is protected by filter_mutex. This leads to the race: echo 'bar == 0 || bar == 10' \ | > sample/filter | | insmod sample.ko add_pred("bar == 0") | -> n_preds == 1 | add_pred("bar == 100") | -> n_preds == 2 | | rmmod sample.ko | insmod sample.ko add_pred("&&") | -> n_preds == 1 (should be 3) | Now event->filter->preds is corrupted. An then when filter_match_preds() is called, the WARN_ON() in it will be triggered. To avoid the race, we remove filter_mutex, and replace it with event_mutex. [ Impact: prevent corruption of filters by module removing and loading ] Signed-off-by: NLi Zefan <lizf@cn.fujitsu.com> LKML-Reference: <4A375A4D.6000205@cn.fujitsu.com> Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>
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