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authorPeter Zijlstra <peterz@infradead.org>2018-01-22 13:39:47 +0300
committerIngo Molnar <mingo@kernel.org>2018-01-24 11:58:18 +0300
commita97cb0e7b3f4c6297fd857055ae8e895f402f501 (patch)
tree151e5f21004fff7210c454a8d8e18d5ed872b2ba /kernel
parent1f07476ec143bbed7bf0b641749783b1094b4c4f (diff)
downloadlinux-a97cb0e7b3f4c6297fd857055ae8e895f402f501.tar.xz
futex: Fix OWNER_DEAD fixup
Both Geert and DaveJ reported that the recent futex commit: c1e2f0eaf015 ("futex: Avoid violating the 10th rule of futex") introduced a problem with setting OWNER_DEAD. We set the bit on an uninitialized variable and then entirely optimize it away as a dead-store. Move the setting of the bit to where it is more useful. Reported-by: Geert Uytterhoeven <geert@linux-m68k.org> Reported-by: Dave Jones <davej@codemonkey.org.uk> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Paul E. McKenney <paulmck@us.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Fixes: c1e2f0eaf015 ("futex: Avoid violating the 10th rule of futex") Link: http://lkml.kernel.org/r/20180122103947.GD2228@hirez.programming.kicks-ass.net Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/futex.c6
1 files changed, 3 insertions, 3 deletions
diff --git a/kernel/futex.c b/kernel/futex.c
index 8c5424dd5924..7f719d110908 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -2311,9 +2311,6 @@ static int fixup_pi_state_owner(u32 __user *uaddr, struct futex_q *q,
raw_spin_lock_irq(&pi_state->pi_mutex.wait_lock);
oldowner = pi_state->owner;
- /* Owner died? */
- if (!pi_state->owner)
- newtid |= FUTEX_OWNER_DIED;
/*
* We are here because either:
@@ -2374,6 +2371,9 @@ retry:
}
newtid = task_pid_vnr(newowner) | FUTEX_WAITERS;
+ /* Owner died? */
+ if (!pi_state->owner)
+ newtid |= FUTEX_OWNER_DIED;
if (get_futex_value_locked(&uval, uaddr))
goto handle_fault;