wait: Fix __wait_event_hrtimeout for RT/DL tasks
authorJuri Lelli <juri.lelli@redhat.com>
Mon, 27 Jun 2022 09:50:51 +0000 (11:50 +0200)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Wed, 17 Aug 2022 12:23:01 +0000 (14:23 +0200)
commit8df06a2753387697a4b2d9289e471c2b5dcc7fe8
tree8161670c39280059a5b308df5a5c5f4c654d2493
parentf0d66189d1618c7af3b040bb44af277e492ce61b
wait: Fix __wait_event_hrtimeout for RT/DL tasks

[ Upstream commit cceeeb6a6d02e7b9a74ddd27a3225013b34174aa ]

Changes to hrtimer mode (potentially made by __hrtimer_init_sleeper on
PREEMPT_RT) are not visible to hrtimer_start_range_ns, thus not
accounted for by hrtimer_start_expires call paths. In particular,
__wait_event_hrtimeout suffers from this problem as we have, for
example:

fs/aio.c::read_events
  wait_event_interruptible_hrtimeout
    __wait_event_hrtimeout
      hrtimer_init_sleeper_on_stack <- this might "mode |= HRTIMER_MODE_HARD"
                                       on RT if task runs at RT/DL priority
        hrtimer_start_range_ns
          WARN_ON_ONCE(!(mode & HRTIMER_MODE_HARD) ^ !timer->is_hard)
          fires since the latter doesn't see the change of mode done by
          init_sleeper

Fix it by making __wait_event_hrtimeout call hrtimer_sleeper_start_expires,
which is aware of the special RT/DL case, instead of hrtimer_start_range_ns.

Reported-by: Bruno Goncalves <bgoncalv@redhat.com>
Signed-off-by: Juri Lelli <juri.lelli@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Daniel Bristot de Oliveira <bristot@kernel.org>
Reviewed-by: Valentin Schneider <vschneid@redhat.com>
Link: https://lore.kernel.org/r/20220627095051.42470-1-juri.lelli@redhat.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
include/linux/wait.h