panic: Reenable preemption in WARN slowpath

[ Upstream commit cccd32816506cbac3a4c65d9dff51b3125ef1a03 ]

Commit:

  5a5d7e9badd2 ("cpuidle: lib/bug: Disable rcu_is_watching() during WARN/BUG")

amended warn_slowpath_fmt() to disable preemption until the WARN splat
has been emitted.

However the commit neglected to reenable preemption in the !fmt codepath,
i.e. when a WARN splat is emitted without additional format string.

One consequence is that users may see more splats than intended.  E.g. a
WARN splat emitted in a work item results in at least two extra splats:

  BUG: workqueue leaked lock or atomic
  (emitted by process_one_work())

  BUG: scheduling while atomic
  (emitted by worker_thread() -> schedule())

Ironically the point of the commit was to *avoid* extra splats. ;)

Fix it.

Fixes: 5a5d7e9badd2 ("cpuidle: lib/bug: Disable rcu_is_watching() during WARN/BUG")
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Paul E. McKenney <paulmck@kernel.org>
Link: https://lore.kernel.org/r/3ec48fde01e4ee6505f77908ba351bad200ae3d1.1694763684.git.lukas@wunner.de
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/kernel/panic.c b/kernel/panic.c
index ca5452afb456dfd15f47aa8d758522b3c5e0022e..63e94f3bd8dcda37c2edc27547131d13c786799a 100644 (file)
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -695,6 +695,7 @@ void warn_slowpath_fmt(const char *file, int line, unsigned taint,
        if (!fmt) {
                __warn(file, line, __builtin_return_address(0), taint,
                       NULL, NULL);
+               warn_rcu_exit(rcu);
                return;
        }