The patch titled
Subject: coredump: change wait_for_dump_helpers() to use wait_event_interruptible()
has been added to the -mm tree. Its filename is
coredump-change-wait_for_dump_helpers-to-use-wait_event_interruptible.patch
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From: Oleg Nesterov <oleg@xxxxxxxxxx>
Subject: coredump: change wait_for_dump_helpers() to use wait_event_interruptible()
wait_for_dump_helpers() calls wake_up/kill_fasync from inside the
wait_event-like loop. This is not needed and in fact this is not strictly
correct, we can/should do this only once after we change pipe->writers.
We could even check if it becomes zero.
Change this code to use use wait_event_interruptible(), this can also help
to make this wait freezable.
With this patch we check pipe->readers without pipe_lock(), this is fine.
Once we see pipe->readers == 1 we know that the handler decremented the
counter, this is all we need.
Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Acked-by: Mandeep Singh Baines <msb@xxxxxxxxxxxx>
Cc: Neil Horman <nhorman@xxxxxxxxxx>
Cc: "Rafael J. Wysocki" <rjw@xxxxxxx>
Cc: Tejun Heo <tj@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/coredump.c | 15 +++++++++------
1 file changed, 9 insertions(+), 6 deletions(-)
diff -puN fs/coredump.c~coredump-change-wait_for_dump_helpers-to-use-wait_event_interruptible fs/coredump.c
--- a/fs/coredump.c~coredump-change-wait_for_dump_helpers-to-use-wait_event_interruptible
+++ a/fs/coredump.c
@@ -439,17 +439,20 @@ static void wait_for_dump_helpers(struct
pipe_lock(pipe);
pipe->readers++;
pipe->writers--;
+ wake_up_interruptible_sync(&pipe->wait);
+ kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
+ pipe_unlock(pipe);
- while ((pipe->readers > 1) && (!signal_pending(current))) {
- wake_up_interruptible_sync(&pipe->wait);
- kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
- pipe_wait(pipe);
- }
+ /*
+ * We actually want wait_event_freezable() but then we need
+ * to clear TIF_SIGPENDING and improve dump_interrupted().
+ */
+ wait_event_interruptible(pipe->wait, pipe->readers == 1);
+ pipe_lock(pipe);
pipe->readers--;
pipe->writers++;
pipe_unlock(pipe);
-
}
/*
_
Patches currently in -mm which might be from oleg@xxxxxxxxxx are
thinkpad-acpi-kill-hotkey_thread_mutex.patch
lockdep-introduce-lock_acquire_exclusive-shared-helper-macros.patch
lglock-update-lockdep-annotations-to-report-recursive-local-locks.patch
ptrace-add-ability-to-retrieve-signals-without-removing-from-a-queue-v4.patch
selftest-add-a-test-case-for-ptrace_peeksiginfo.patch
coredump-only-sigkill-should-interrupt-the-coredumping-task.patch
coredump-ensure-that-sigkill-always-kills-the-dumping-thread.patch
coredump-sanitize-the-setting-of-signal-group_exit_code.patch
coredump-introduce-dump_interrupted.patch
coredump-factor-out-the-setting-of-pf_dumpcore.patch
coredump-change-wait_for_dump_helpers-to-use-wait_event_interruptible.patch
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