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| author | Peter Zijlstra <peterz@infradead.org> | 2018-01-22 11:39:47 +0100 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2018-01-24 09:58:18 +0100 |
| commit | a97cb0e7b3f4c6297fd857055ae8e895f402f501 (patch) | |
| tree | 151e5f21004fff7210c454a8d8e18d5ed872b2ba /kernel/futex.c | |
| parent | 1f07476ec143bbed7bf0b641749783b1094b4c4f (diff) | |
| download | lwn-a97cb0e7b3f4c6297fd857055ae8e895f402f501.tar.gz lwn-a97cb0e7b3f4c6297fd857055ae8e895f402f501.zip | |
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/futex.c')
| -rw-r--r-- | kernel/futex.c | 6 |
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; |