From: Thomas Gleixner <tglx@linutronix.de>
To: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Sebastian Sewior <bigeasy@linutronix.de>,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@kernel.org>,
Martin Schwidefsky <schwidefsky@de.ibm.com>,
LKML <linux-kernel@vger.kernel.org>,
linux-s390@vger.kernel.org, Stefan Liebler <stli@linux.ibm.com>
Subject: Re: WARN_ON_ONCE(!new_owner) within wake_futex_pi() triggered
Date: Wed, 30 Jan 2019 13:15:18 +0100 (CET) [thread overview]
Message-ID: <alpine.DEB.2.21.1901301303320.5537@nanos.tec.linutronix.de> (raw)
In-Reply-To: <20190130094913.GC5299@osiris>
On Wed, 30 Jan 2019, Heiko Carstens wrote:
> On Tue, Jan 29, 2019 at 06:16:53PM +0100, Sebastian Sewior wrote:
> > if (unlikely(p->flags & PF_KTHREAD)) {
> > put_task_struct(p);
>
> Last lines of the trace with your additional patch (full log attached):
>
> <...>-50539 [003] .... 2376.398223: sys_futex -> 0x0
> <...>-50539 [003] .... 2376.398223: sys_futex(uaddr: 3ffb7700208, op: 6, val: 1, utime: 0, uaddr2: 3, val3: 0)
> <...>-50539 [003] .... 2376.398225: attach_to_pi_owner: Missing pid 50734
> <...>-50539 [003] .... 2376.398226: handle_exit_race: uval2 vs uval 8000c62e vs 8000c62e (-1)
So the user space value is: 8000c62e. FUTEX_WAITER bit is set and the owner
of the futex is PID 50734, which exited long time ago:
<...>-50734 [000] .... 2376.394936: sched_process_exit: comm=ld64.so.1 pid=50734 prio=120
But at least from the kernel view 50734 has released it last:
<...>-50734 [000] .... 2376.394930: sys_futex(uaddr: 3ffb7700208, op: 7, val: 3ff00000007, utime: 3ffb3ef8910, uaddr2: 3ffb3ef8910, val3: 3ffc0afe987)
<...>-50539 [003] .... 2376.398223: sys_futex(uaddr: 3ffb7700208, op: 6, val: 1, utime: 0, uaddr2: 3, val3: 0)
Now, if it would have acquired it in userspace again before exiting, then
the robust list exit code should have set the OWNER_DIED bit as well, but
that's not set....
debug patch for the robust list exit handling below.
Thanks,
tglx
8<-----------------
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -3440,10 +3440,13 @@ static int handle_futex_death(u32 __user
{
u32 uval, uninitialized_var(nval), mval;
+ trace_printk("uaddr: %lx pi: %d\n", (unsigned long) uaddr, pi);
retry:
if (get_user(uval, uaddr))
return -1;
+ trace_printk("uaddr: %lx uval: %08x\n", (unsigned long) uaddr, uval);
+
if ((uval & FUTEX_TID_MASK) == task_pid_vnr(curr)) {
/*
* Ok, this dying thread is truly holding a futex
@@ -3480,6 +3483,7 @@ static int handle_futex_death(u32 __user
if (!pi && (uval & FUTEX_WAITERS))
futex_wake(uaddr, 1, 1, FUTEX_BITSET_MATCH_ANY);
}
+ trace_printk("uaddr: %lx success\n", (unsigned long) uaddr);
return 0;
}
next prev parent reply other threads:[~2019-01-30 12:15 UTC|newest]
Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-27 8:11 WARN_ON_ONCE(!new_owner) within wake_futex_pi() triggered Heiko Carstens
2018-11-28 14:32 ` Thomas Gleixner
2018-11-29 11:23 ` Heiko Carstens
2019-01-21 12:21 ` Heiko Carstens
2019-01-21 13:12 ` Thomas Gleixner
2019-01-22 21:14 ` Thomas Gleixner
2019-01-23 9:24 ` Heiko Carstens
2019-01-23 12:33 ` Thomas Gleixner
2019-01-23 12:40 ` Heiko Carstens
2019-01-28 13:44 ` Peter Zijlstra
2019-01-28 13:58 ` Peter Zijlstra
2019-01-28 15:53 ` Thomas Gleixner
2019-01-29 8:49 ` Peter Zijlstra
2019-01-29 22:15 ` [PATCH] futex: Handle early deadlock return correctly Thomas Gleixner
2019-01-30 12:01 ` Thomas Gleixner
2019-02-08 12:05 ` [tip:locking/urgent] " tip-bot for Thomas Gleixner
2019-01-29 9:01 ` WARN_ON_ONCE(!new_owner) within wake_futex_pi() triggered Heiko Carstens
2019-01-29 9:33 ` Peter Zijlstra
2019-01-29 9:45 ` Thomas Gleixner
2019-01-29 10:24 ` Heiko Carstens
2019-01-29 10:35 ` Peter Zijlstra
2019-01-29 13:03 ` Thomas Gleixner
2019-01-29 13:23 ` Heiko Carstens
[not found] ` <20190129151058.GG26906@osiris>
2019-01-29 17:16 ` Sebastian Sewior
2019-01-29 21:45 ` Thomas Gleixner
[not found] ` <20190130094913.GC5299@osiris>
2019-01-30 12:15 ` Thomas Gleixner [this message]
[not found] ` <20190130125955.GD5299@osiris>
2019-01-30 13:24 ` Sebastian Sewior
2019-01-30 13:29 ` Thomas Gleixner
2019-01-30 14:33 ` Thomas Gleixner
2019-01-30 17:56 ` Thomas Gleixner
2019-01-30 21:07 ` Sebastian Sewior
2019-01-30 23:13 ` WARN_ON_ONCE(!new_owner) within wake_futex_pi() triggerede Thomas Gleixner
2019-01-30 23:35 ` Paul E. McKenney
2019-01-30 23:55 ` Thomas Gleixner
2019-01-31 0:27 ` Thomas Gleixner
2019-01-31 1:45 ` Paul E. McKenney
2019-01-31 16:52 ` Heiko Carstens
2019-01-31 17:06 ` Sebastian Sewior
2019-01-31 20:42 ` Heiko Carstens
2019-02-01 16:12 ` Heiko Carstens
2019-02-01 21:59 ` Thomas Gleixner
[not found] ` <20190202091043.GA3381@osiris>
2019-02-02 10:14 ` Thomas Gleixner
2019-02-02 11:20 ` Heiko Carstens
2019-02-03 16:30 ` Thomas Gleixner
2019-02-04 11:40 ` Heiko Carstens
2019-01-31 1:44 ` Paul E. McKenney
2019-01-30 13:25 ` WARN_ON_ONCE(!new_owner) within wake_futex_pi() triggered Thomas Gleixner
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