Messages in this thread Patch in this message | | | Date | Thu, 22 Apr 2021 21:44:22 +0200 | From | Thomas Gleixner <> | Subject | [patch 5/6] futex: Prepare futex_lock_pi() for runtime clock selection |
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futex_lock_pi() is the only futex operation which cannot select the clock for timeouts (CLOCK_MONOTONIC/CLOCK_REALTIME). That's inconsistent and there is no particular reason why this cannot be supported.
This was overlooked when CLOCK_REALTIME_FLAG was introduced and unfortunately not reported when the inconsistency was discovered in glibc.
Prepare the function and enforce the CLOCK_REALTIME_FLAG on FUTEX_LOCK_PI so that a new FUTEX_LOCK_PI2 can implement it correctly.
Reported-by: Kurt Kanzenbach <kurt@linutronix.de> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> --- kernel/futex.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)
--- a/kernel/futex.c +++ b/kernel/futex.c @@ -2786,7 +2786,7 @@ static int futex_lock_pi(u32 __user *uad if (refill_pi_state_cache()) return -ENOMEM; - to = futex_setup_timer(time, &timeout, FLAGS_CLOCKRT, 0); + to = futex_setup_timer(time, &timeout, flags, 0); retry: ret = get_futex_key(uaddr, flags & FLAGS_SHARED, &q.key, FUTEX_WRITE); @@ -3711,7 +3711,7 @@ long do_futex(u32 __user *uaddr, int op, if (op & FUTEX_CLOCK_REALTIME) { flags |= FLAGS_CLOCKRT; - if (cmd != FUTEX_WAIT_BITSET && cmd != FUTEX_WAIT_REQUEUE_PI) + if (cmd != FUTEX_WAIT_BITSET && cmd != FUTEX_WAIT_REQUEUE_PI) return -ENOSYS; } @@ -3743,6 +3743,7 @@ long do_futex(u32 __user *uaddr, int op, case FUTEX_WAKE_OP: return futex_wake_op(uaddr, flags, uaddr2, val, val2, val3); case FUTEX_LOCK_PI: + flags |= FLAGS_CLOCKRT; return futex_lock_pi(uaddr, flags, timeout, 0); case FUTEX_UNLOCK_PI: return futex_unlock_pi(uaddr, flags);
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