lkml.org 
[lkml]   [2018]   [May]   [22]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
Subjectwrite_lock_irq(&tasklist_lock)
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

\
 
 \ /
  Last update: 2018-05-22 21:41    [W:1.778 / U:0.092 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site