From: Juri Lelli juri.lelli@redhat.com
[ 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 | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-)
diff --git a/include/linux/wait.h b/include/linux/wait.h index 9b8b0833100a..1663e47681a3 100644 --- a/include/linux/wait.h +++ b/include/linux/wait.h @@ -534,10 +534,11 @@ do { \ \ hrtimer_init_sleeper_on_stack(&__t, CLOCK_MONOTONIC, \ HRTIMER_MODE_REL); \ - if ((timeout) != KTIME_MAX) \ - hrtimer_start_range_ns(&__t.timer, timeout, \ - current->timer_slack_ns, \ - HRTIMER_MODE_REL); \ + if ((timeout) != KTIME_MAX) { \ + hrtimer_set_expires_range_ns(&__t.timer, timeout, \ + current->timer_slack_ns); \ + hrtimer_sleeper_start_expires(&__t, HRTIMER_MODE_REL); \ + } \ \ __ret = ___wait_event(wq_head, condition, state, 0, 0, \ if (!__t.task) { \