From: "Edgecombe, Rick P" <rick.p.edgecombe@intel.com>
To: "peterz@infradead.org" <peterz@infradead.org>
Cc: "xry111@xry111.site" <xry111@xry111.site>,
"andrealmeid@igalia.com" <andrealmeid@igalia.com>,
"fweimer@redhat.com" <fweimer@redhat.com>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
"libc-alpha@sourceware.org" <libc-alpha@sourceware.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"tglx@linutronix.de" <tglx@linutronix.de>,
"linux-api@vger.kernel.org" <linux-api@vger.kernel.org>,
"linux-arch@vger.kernel.org" <linux-arch@vger.kernel.org>
Subject: Re: Several tst-robust* tests time out with recent Linux kernel
Date: Fri, 17 Nov 2023 01:22:56 +0000 [thread overview]
Message-ID: <158f6a47727a40c163e3fa6041a24388549c68f2.camel@intel.com> (raw)
In-Reply-To: <564119521b61b5a38f9bdfe6c7a41fcbb07049c9.camel@intel.com>
A bit more info...
The error returned to userspace is originating from:
https://github.com/torvalds/linux/blob/master/kernel/futex/pi.c#L295
'uval' is often zero in that error case, but sometimes just a
mismatching value like: uval=0x567, task_pid_vnr()=0x564
Depending on the number of CPUs the VM is running on it reproduces or
not. When it does reproduce, the newly added path here is taken:
https://github.com/torvalds/linux/blob/master/kernel/futex/pi.c#L1185
The path is taken a lot during the test, sometimes >400 times before
the above linked error is generated during the syscall. When it doesn't
reproduce, I never saw that new path taken.
More print statements make the reproduction less reliable, so it does
seem to have a race in the mix at least somewhat. Otherwise, I haven't
tried to understand what is going on here with all this highwire
locking.
Hope it helps.
next prev parent reply other threads:[~2023-11-17 1:23 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <4bda9f2e06512e375e045f9e72edb205104af19c.camel@xry111.site>
2023-11-14 9:46 ` Several tst-robust* tests time out with recent Linux kernel Xi Ruoyao
2023-11-14 15:31 ` Peter Zijlstra
2023-11-14 15:40 ` Peter Zijlstra
2023-11-14 16:43 ` Florian Weimer
2023-11-14 20:14 ` Peter Zijlstra
2023-11-15 1:11 ` Edgecombe, Rick P
2023-11-15 8:51 ` Peter Zijlstra
2023-11-15 23:28 ` Edgecombe, Rick P
2023-11-17 1:22 ` Edgecombe, Rick P [this message]
2024-01-19 13:56 ` Stefan Liebler
2024-01-29 22:23 ` Edgecombe, Rick P
2024-01-30 10:12 ` Stefan Liebler
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