From: Sodagudi Prasad <psodagud@codeaurora.org>
To: keescook@chromium.org, luto@amacapital.net, wad@chromium.org,
akpm@linux-foundation.org, riel@redhat.com, tglx@linutronix.de,
mingo@kernel.org, peterz@infradead.org, ebiggers@google.com,
fweisbec@gmail.com, sherryy@android.com,
vegard.nossum@oracle.com, cl@linux.com, aarcange@redhat.com,
alexander.levin@verizon.com, vegard.nossum@oracle.com,
sherryy@android.com, fweisbec@gmail.com, ebiggers@google.com,
peterz@infradead.org
Cc: linux-kernel@vger.kernel.org, torvalds@linux-foundation.org
Subject: write_lock_irq(&tasklist_lock)
Date: Tue, 22 May 2018 12:40:05 -0700 [thread overview]
Message-ID: <0879f797135033e05e8e9166a3c85628@codeaurora.org> (raw)
Hi All,
When following test is executed on 4.14.41 stable kernel, observed that
one of the core is waiting for tasklist_lock for long time with IRQs
disabled.
./stress-ng-64 --get 8 -t 3h --times --metrics-brief
Every time when device is crashed, I observed that one the task stuck at
fork system call and waiting for tasklist_lock as writer with irq
disabled.
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git/tree/kernel/fork.c?h=linux-4.14.y#n1843
Some other tasks are making getrlimit, prlimit system calls, so that
these readers are continuously taking tasklist_list read lock.
Writer has disabled local IRQs for long time and waiting to readers to
finish but readers are keeping tasklist_lock busy
for quite long time.
I think, −−get N option creates N thread and they make following system
calls.
========================================================================
start N workers that call system calls that fetch data from the kernel,
currently these are: getpid,
getppid, getcwd, getgid, getegid, getuid, getgroups, getpgrp, getpgid,
getpriority, getresgid, getresuid,
getrlimit, prlimit, getrusage, getsid, gettid, getcpu, gettimeofday,
uname, adjtimex, sysfs.
Some of these system calls are OS specific.
========================================================================
Have you observed this type of issues with tasklist_lock ?
Do we need write_lock_irq(&tasklist_lock) in below portion of code ? Can
I use write_unlock instead of write_lock_irq in portion of code?
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git/tree/kernel/fork.c?h=linux-4.14.y#n1843
-Thanks, Prasad
--
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora
Forum,
Linux Foundation Collaborative Project
next reply other threads:[~2018-05-22 19:40 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-05-22 19:40 Sodagudi Prasad [this message]
2018-05-22 20:27 ` write_lock_irq(&tasklist_lock) Linus Torvalds
2018-05-22 21:17 ` write_lock_irq(&tasklist_lock) Peter Zijlstra
2018-05-22 21:31 ` write_lock_irq(&tasklist_lock) Linus Torvalds
2018-05-23 8:19 ` write_lock_irq(&tasklist_lock) Peter Zijlstra
2018-05-23 13:05 ` write_lock_irq(&tasklist_lock) Will Deacon
2018-05-23 15:25 ` write_lock_irq(&tasklist_lock) Linus Torvalds
2018-05-23 15:36 ` write_lock_irq(&tasklist_lock) Will Deacon
2018-05-23 16:26 ` write_lock_irq(&tasklist_lock) Linus Torvalds
2018-05-24 12:49 ` write_lock_irq(&tasklist_lock) Will Deacon
2018-05-24 13:51 ` write_lock_irq(&tasklist_lock) Boqun Feng
2018-05-24 17:37 ` write_lock_irq(&tasklist_lock) Sodagudi Prasad
2018-05-24 18:28 ` write_lock_irq(&tasklist_lock) Peter Zijlstra
2018-05-24 21:14 ` write_lock_irq(&tasklist_lock) Andrea Parri
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