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    Subject[PATCH 5.4 057/389] wait: Fix __wait_event_hrtimeout for RT/DL tasks
    Date
    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 5903b1d17c92..7d04c1b588c7 100644
    --- a/include/linux/wait.h
    +++ b/include/linux/wait.h
    @@ -529,10 +529,11 @@ 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) { \
    --
    2.35.1


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