From: tip-bot for Peter Zijlstra <tipbot@zytor.com>
To: linux-tip-commits@vger.kernel.org
Cc: peterz@infradead.org, hpa@zytor.com, geert@linux-m68k.org,
tglx@linutronix.de, akpm@linux-foundation.org, mingo@kernel.org,
paulmck@us.ibm.com, linux-kernel@vger.kernel.org,
torvalds@linux-foundation.org, davej@codemonkey.org.uk
Subject: [tip:locking/urgent] futex: Fix OWNER_DEAD fixup
Date: Wed, 24 Jan 2018 02:37:55 -0800 [thread overview]
Message-ID: <tip-a97cb0e7b3f4c6297fd857055ae8e895f402f501@git.kernel.org> (raw)
In-Reply-To: <20180122103947.GD2228@hirez.programming.kicks-ass.net>
Commit-ID: a97cb0e7b3f4c6297fd857055ae8e895f402f501
Gitweb: https://git.kernel.org/tip/a97cb0e7b3f4c6297fd857055ae8e895f402f501
Author: Peter Zijlstra <peterz@infradead.org>
AuthorDate: Mon, 22 Jan 2018 11:39:47 +0100
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Wed, 24 Jan 2018 09:58:18 +0100
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>
---
kernel/futex.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/kernel/futex.c b/kernel/futex.c
index 8c5424d..7f719d1 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;
prev parent reply other threads:[~2018-01-24 10:43 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-17 15:24 [GIT PULL] locking fixes Ingo Molnar
2018-01-22 9:43 ` Geert Uytterhoeven
2018-01-22 10:39 ` Peter Zijlstra
2018-01-23 16:19 ` [PATCH] futex: Fix OWNER_DEAD fixup Peter Zijlstra
2018-01-24 10:37 ` tip-bot for Peter Zijlstra [this message]
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