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tracing: Wake up poll waiters for hist files when removing an event

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JIRA: https://issues.redhat.com/browse/RHEL-151695

commit 9678e53179aa7e907360f5b5b275769008a69b80
Author: Petr Pavlu <petr.pavlu@suse.com>
Date:   Thu Feb 19 17:27:02 2026 +0100

    tracing: Wake up poll waiters for hist files when removing an event

    The event_hist_poll() function attempts to verify whether an event file is
    being removed, but this check may not occur or could be unnecessarily
    delayed. This happens because hist_poll_wakeup() is currently invoked only
    from event_hist_trigger() when a hist command is triggered. If the event
    file is being removed, no associated hist command will be triggered and a
    waiter will be woken up only after an unrelated hist command is triggered.

    Fix the issue by adding a call to hist_poll_wakeup() in
    remove_event_file_dir() after setting the EVENT_FILE_FL_FREED flag. This
    ensures that a task polling on a hist file is woken up and receives
    EPOLLERR.

    Cc: stable@vger.kernel.org
    Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
    Cc: Tom Zanussi <zanussi@kernel.org>
    Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
    Link: https://patch.msgid.link/20260219162737.314231-3-petr.pavlu@suse.com
    Fixes: 1bd13edbbed6 ("tracing/hist: Add poll(POLLIN) support on hist file")
    Signed-off-by: Petr Pavlu <petr.pavlu@suse.com>
    Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

Signed-off-by: Jerome Marchand <jmarchan@redhat.com>
This commit is contained in:
Jerome Marchand
2026-03-06 09:28:24 +01:00
parent 6ad6f3619c
commit 9ac8752720
2 changed files with 8 additions and 0 deletions
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include/linux/trace_events.h
+5
View File
@@ -690,6 +690,11 @@ static inline void hist_poll_wakeup(void)
#define hist_poll_wait(file, wait) \
poll_wait(file, &hist_poll_wq, wait)
#else
static inline void hist_poll_wakeup(void)
{
}
#endif
#define __TRACE_EVENT_FLAGS(name, value) \
kernel/trace/trace_events.c
+3
View File
@@ -1169,6 +1169,9 @@ static void remove_event_file_dir(struct trace_event_file *file)
free_event_filter(file->filter);
file->flags |= EVENT_FILE_FL_FREED;
event_file_put(file);
/* Wake up hist poll waiters to notice the EVENT_FILE_FL_FREED flag. */
hist_poll_wakeup();
}
/*