Messages in this thread Patch in this message | | | From | Zheng Yejian <> | Subject | [PATCH 4.9.257 1/1] futex: Fix OWNER_DEAD fixup | Date | Mon, 22 Feb 2021 19:05:42 +0800 |
| |
From: Peter Zijlstra <peterz@infradead.org>
commit a97cb0e7b3f4c6297fd857055ae8e895f402f501 upstream.
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> Signed-off-by: Zheng Yejian <zhengyejian1@huawei.com> --- kernel/futex.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-)
diff --git a/kernel/futex.c b/kernel/futex.c index 83db5787c67e..7cb2baa9446a 100644 --- a/kernel/futex.c +++ b/kernel/futex.c @@ -2283,10 +2283,6 @@ static int __fixup_pi_state_owner(u32 __user *uaddr, struct futex_q *q, oldowner = pi_state->owner; - /* Owner died? */ - if (!pi_state->owner) - newtid |= FUTEX_OWNER_DIED; - /* * We are here because either: * @@ -2344,6 +2340,9 @@ static int __fixup_pi_state_owner(u32 __user *uaddr, struct futex_q *q, } 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; -- 2.25.4
| |