Messages in this thread Patch in this message | | | From | Juri Lelli <> | Subject | [PATCH] linux/wait: Fix __wait_event_hrtimeout for RT/DL tasks | Date | Mon, 27 Jun 2022 11:50:51 +0200 |
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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.
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Reported-by: Bruno Goncalves <bgoncalv@redhat.com> Signed-off-by: Juri Lelli <juri.lelli@redhat.com>
--- This is a continuation of discussion happened at https://lore.kernel.org/lkml/YqnygxNWOztakt8+@localhost.localdomain/ "[RT] WARNING at hrtimer_start_range_ns" --- 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 851e07da2583..58cfbf81447c 100644 --- a/include/linux/wait.h +++ b/include/linux/wait.h @@ -544,10 +544,11 @@ 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) { \ -- 2.36.1
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