From: Peter Zijlstra <peterz@infradead.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: "Holger Hoffstätte" <holger@applied-asynchrony.com>,
"Qi Zheng" <zhengqi.arch@bytedance.com>,
"Kees Cook" <keescook@chromium.org>,
"Thomas Gleixner" <tglx@linutronix.de>,
"Justin Forbes" <jmforbes@linuxtx.org>,
"Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
"Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>,
"Andrew Morton" <akpm@linux-foundation.org>,
"Guenter Roeck" <linux@roeck-us.net>,
"Shuah Khan" <shuah@kernel.org>,
patches@kernelci.org, lkft-triage@lists.linaro.org,
"Pavel Machek" <pavel@denx.de>,
"Jon Hunter" <jonathanh@nvidia.com>,
"Florian Fainelli" <f.fainelli@gmail.com>,
stable <stable@vger.kernel.org>,
"Josh Poimboeuf" <jpoimboe@redhat.com>
Subject: Re: [PATCH 5.15 000/923] 5.15.3-rc3 review
Date: Thu, 18 Nov 2021 09:18:52 +0100 [thread overview]
Message-ID: <20211118081852.GM174730@worktop.programming.kicks-ass.net> (raw)
In-Reply-To: <20211118080627.GH174703@worktop.programming.kicks-ass.net>
On Thu, Nov 18, 2021 at 09:06:27AM +0100, Peter Zijlstra wrote:
> On Wed, Nov 17, 2021 at 03:50:17PM -0800, Linus Torvalds wrote:
>
> > I really don't think the WCHAN code should use unwinders at all. It's
> > too damn fragile, and it's too easily triggered from user space.
>
> On x86, esp. with ORC, it pretty much has to. The thing is, the ORC
> unwinder has been very stable so far. I'm guessing there's some really
> stupid thing going on, like for example trying to unwind a freed stack.
>
> I *just* managed to reproduce, so let me go have a poke.
Confirmed, with the below it no longer reproduces. Now, let me go undo
that and fix the unwinder to not explode while trying to unwind nothing.
---
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 862af1db22ab..f810c5192cb9 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1978,7 +1978,7 @@ unsigned long get_wchan(struct task_struct *p)
raw_spin_lock_irq(&p->pi_lock);
state = READ_ONCE(p->__state);
smp_rmb(); /* see try_to_wake_up() */
- if (state != TASK_RUNNING && state != TASK_WAKING && !p->on_rq)
+ if (state != TASK_RUNNING && state != TASK_WAKING && !p->on_rq && !(p->flags & PF_EXITING))
ip = __get_wchan(p);
raw_spin_unlock_irq(&p->pi_lock);
next prev parent reply other threads:[~2021-11-18 8:19 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-17 10:19 [PATCH 5.15 000/923] 5.15.3-rc3 review Greg Kroah-Hartman
2021-11-17 13:37 ` Fox Chen
2021-11-17 14:13 ` Guenter Roeck
2021-11-17 14:43 ` Greg Kroah-Hartman
2021-11-17 14:54 ` Guenter Roeck
2021-11-17 17:34 ` Jon Hunter
2021-11-17 18:51 ` Florian Fainelli
2021-11-17 20:25 ` Holger Kiehl
2021-11-18 8:14 ` Greg Kroah-Hartman
2021-11-18 14:08 ` Holger Kiehl
2021-11-18 17:08 ` Greg Kroah-Hartman
2021-11-17 20:35 ` Guenter Roeck
2021-11-17 21:32 ` Justin Forbes
2021-11-17 23:32 ` Holger Hoffstätte
2021-11-17 23:50 ` Linus Torvalds
2021-11-18 0:16 ` Kees Cook
2021-11-18 6:26 ` Guenter Roeck
2021-11-18 8:14 ` Greg Kroah-Hartman
2021-11-18 8:12 ` Greg Kroah-Hartman
2021-11-18 17:17 ` Kees Cook
2021-11-18 8:06 ` Peter Zijlstra
2021-11-18 8:18 ` Peter Zijlstra [this message]
2021-11-18 9:39 ` Peter Zijlstra
2021-11-18 10:12 ` Peter Zijlstra
2021-11-18 12:11 ` Peter Zijlstra
2021-11-19 2:04 ` Josh Poimboeuf
2021-11-19 9:29 ` [PATCH] x86: Pin task-stack in __get_wchan() Peter Zijlstra
2021-11-19 10:02 ` Qi Zheng
2021-11-19 10:22 ` Peter Zijlstra
2021-11-19 10:26 ` Qi Zheng
2021-11-19 18:16 ` Linus Torvalds
2021-11-19 18:35 ` Josh Poimboeuf
2021-11-22 9:32 ` Peter Zijlstra
2021-11-22 16:14 ` Josh Poimboeuf
2021-11-18 5:45 ` [PATCH 5.15 000/923] 5.15.3-rc3 review Naresh Kamboju
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