From: Peter Zijlstra <peterz@infradead.org>
To: Darren Hart <dvhart@infradead.org>
Cc: tglx@linutronix.de, mingo@kernel.org, juri.lelli@arm.com,
rostedt@goodmis.org, xlpang@redhat.com, bigeasy@linutronix.de,
linux-kernel@vger.kernel.org, mathieu.desnoyers@efficios.com,
jdesfossez@efficios.com, bristot@redhat.com
Subject: Re: [PATCH -v6 13/13] futex: futex_lock_pi() vs PREEMPT_RT_FULL
Date: Mon, 10 Apr 2017 11:08:18 +0200 [thread overview]
Message-ID: <20170410090818.ztb2fxzb6oy3ee7o@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20170408022610.GC16143@fury>
On Fri, Apr 07, 2017 at 07:26:10PM -0700, Darren Hart wrote:
> Peter, I presume there will be a v7 with the u32 change and hopefully a couple
> text updates?
Well, tglx already committed these here patches, so no -v7. What I can
do however is do a follow up patch that fixes some of the in-code things
you mentioned.
Something like the below is what I had lying about from your earlier
emails; I've not looked to see if there's anything else from your later
emails.
---
Subject: futex: Small misc fixes..
From: Peter Zijlstra <peterz@infradead.org>
Date: Fri Apr 7 09:04:07 CEST 2017
Feedback from Darren's review.
Reported-by: Darren Hart (VMWare) <dvhart@infradead.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
kernel/futex.c | 11 +++++++----
1 file changed, 7 insertions(+), 4 deletions(-)
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -1025,7 +1025,8 @@ static int attach_to_pi_state(u32 __user
struct futex_pi_state **ps)
{
pid_t pid = uval & FUTEX_TID_MASK;
- int ret, uval2;
+ u32 uval2;
+ int ret;
/*
* Userspace might have messed up non-PI and PI futexes [3]
@@ -1441,6 +1442,11 @@ static int wake_futex_pi(u32 __user *uad
if (ret)
goto out_unlock;
+ /*
+ * This is a point of no return; once we modify the uval there is no
+ * going back and subsequent operations must not fail.
+ */
+
raw_spin_lock(&pi_state->owner->pi_lock);
WARN_ON(list_empty(&pi_state->list));
list_del_init(&pi_state->list);
@@ -1452,9 +1458,6 @@ static int wake_futex_pi(u32 __user *uad
pi_state->owner = new_owner;
raw_spin_unlock(&new_owner->pi_lock);
- /*
- * We've updated the uservalue, this unlock cannot fail.
- */
postunlock = __rt_mutex_futex_unlock(&pi_state->pi_mutex, &wake_q);
out_unlock:
next prev parent reply other threads:[~2017-04-10 9:08 UTC|newest]
Thread overview: 60+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-03-22 10:35 [PATCH -v6 00/13] The arduous story of FUTEX_UNLOCK_PI Peter Zijlstra
2017-03-22 10:35 ` [PATCH -v6 01/13] futex: Cleanup variable names for futex_top_waiter() Peter Zijlstra
2017-03-23 18:19 ` [tip:locking/core] " tip-bot for Peter Zijlstra
2017-03-24 21:11 ` [PATCH -v6 01/13] " Darren Hart
2017-03-22 10:35 ` [PATCH -v6 02/13] futex: Use smp_store_release() in mark_wake_futex() Peter Zijlstra
2017-03-23 18:19 ` [tip:locking/core] " tip-bot for Peter Zijlstra
2017-03-24 21:16 ` [PATCH -v6 02/13] " Darren Hart
2017-03-22 10:35 ` [PATCH -v6 03/13] futex: Remove rt_mutex_deadlock_account_*() Peter Zijlstra
2017-03-23 18:20 ` [tip:locking/core] " tip-bot for Peter Zijlstra
2017-03-24 21:29 ` [PATCH -v6 03/13] " Darren Hart
2017-03-24 21:31 ` Darren Hart
2017-03-22 10:35 ` [PATCH -v6 04/13] futex,rt_mutex: Provide futex specific rt_mutex API Peter Zijlstra
2017-03-23 18:20 ` [tip:locking/core] " tip-bot for Peter Zijlstra
2017-03-25 0:37 ` [PATCH -v6 04/13] " Darren Hart
2017-04-06 12:15 ` Peter Zijlstra
2017-04-06 17:02 ` Darren Hart
2017-04-05 15:02 ` Darren Hart
2017-04-06 12:17 ` Peter Zijlstra
2017-04-06 17:08 ` Darren Hart
2017-03-22 10:35 ` [PATCH -v6 05/13] futex: Change locking rules Peter Zijlstra
2017-03-23 18:21 ` [tip:locking/core] " tip-bot for Peter Zijlstra
2017-04-05 21:18 ` [PATCH -v6 05/13] " Darren Hart
2017-04-06 12:28 ` Peter Zijlstra
2017-04-06 15:58 ` Joe Perches
2017-04-06 17:21 ` Darren Hart
2017-03-22 10:35 ` [PATCH -v6 06/13] futex: Cleanup refcounting Peter Zijlstra
2017-03-23 18:21 ` [tip:locking/core] " tip-bot for Peter Zijlstra
2017-04-05 21:29 ` [PATCH -v6 06/13] " Darren Hart
2017-03-22 10:35 ` [PATCH -v6 07/13] futex: Rework inconsistent rt_mutex/futex_q state Peter Zijlstra
2017-03-23 18:22 ` [tip:locking/core] " tip-bot for Peter Zijlstra
2017-04-05 21:58 ` [PATCH -v6 07/13] " Darren Hart
2017-03-22 10:35 ` [PATCH -v6 08/13] futex: Pull rt_mutex_futex_unlock() out from under hb->lock Peter Zijlstra
2017-03-23 18:22 ` [tip:locking/core] " tip-bot for Peter Zijlstra
2017-04-05 23:52 ` [PATCH -v6 08/13] " Darren Hart
2017-04-06 12:42 ` Peter Zijlstra
2017-04-06 17:42 ` Darren Hart
2017-03-22 10:35 ` [PATCH -v6 09/13] futex,rt_mutex: Introduce rt_mutex_init_waiter() Peter Zijlstra
2017-03-23 18:23 ` [tip:locking/core] " tip-bot for Peter Zijlstra
2017-04-05 23:57 ` [PATCH -v6 09/13] " Darren Hart
2017-03-22 10:35 ` [PATCH -v6 10/13] futex,rt_mutex: Restructure rt_mutex_finish_proxy_lock() Peter Zijlstra
2017-03-23 18:23 ` [tip:locking/core] " tip-bot for Peter Zijlstra
2017-04-07 23:30 ` [PATCH -v6 10/13] " Darren Hart
2017-04-07 23:35 ` Darren Hart
2017-03-22 10:35 ` [PATCH -v6 11/13] futex: Rework futex_lock_pi() to use rt_mutex_*_proxy_lock() Peter Zijlstra
2017-03-23 18:24 ` [tip:locking/core] " tip-bot for Peter Zijlstra
2017-04-08 0:55 ` [PATCH -v6 11/13] " Darren Hart
2017-04-10 15:51 ` alexander.levin
2017-04-10 16:03 ` Thomas Gleixner
2017-04-14 9:30 ` [tip:locking/core] futex: Avoid freeing an active timer tip-bot for Thomas Gleixner
2017-03-22 10:35 ` [PATCH -v6 12/13] futex: futex_unlock_pi() determinism Peter Zijlstra
2017-03-23 18:24 ` [tip:locking/core] futex: Futex_unlock_pi() determinism tip-bot for Peter Zijlstra
2017-04-08 1:27 ` [PATCH -v6 12/13] futex: futex_unlock_pi() determinism Darren Hart
2017-03-22 10:36 ` [PATCH -v6 13/13] futex: futex_lock_pi() vs PREEMPT_RT_FULL Peter Zijlstra
2017-03-23 18:25 ` [tip:locking/core] futex: Drop hb->lock before enqueueing on the rtmutex tip-bot for Peter Zijlstra
2017-04-08 2:26 ` [PATCH -v6 13/13] futex: futex_lock_pi() vs PREEMPT_RT_FULL Darren Hart
2017-04-08 5:22 ` Mike Galbraith
2017-04-10 8:43 ` Sebastian Andrzej Siewior
2017-04-10 9:08 ` Peter Zijlstra [this message]
2017-04-10 16:05 ` Darren Hart
2017-03-24 1:45 ` [PATCH -v6 00/13] The arduous story of FUTEX_UNLOCK_PI Darren Hart
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