From 9678e53179aa7e907360f5b5b275769008a69b80 Mon Sep 17 00:00:00 2001 From: Petr Pavlu Date: Thu, 19 Feb 2026 17:27:02 +0100 Subject: [PATCH] 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 Cc: Tom Zanussi Acked-by: Masami Hiramatsu (Google) 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 Signed-off-by: Steven Rostedt (Google) --- include/linux/trace_events.h | 5 +++++ kernel/trace/trace_events.c | 3 +++ 2 files changed, 8 insertions(+) diff --git a/include/linux/trace_events.h b/include/linux/trace_events.h index 0a2b8229b999..37eb2f0f3dd8 100644 --- a/include/linux/trace_events.h +++ b/include/linux/trace_events.h @@ -683,6 +683,11 @@ 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) \ diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c index 61fe01dce7a6..b659653dc03a 100644 --- a/kernel/trace/trace_events.c +++ b/kernel/trace/trace_events.c @@ -1311,6 +1311,9 @@ 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(); } /* -- 2.47.3