Messages in this thread | | | Date | Tue, 22 May 2018 12:40:05 -0700 | From | Sodagudi Prasad <> | Subject | write_lock_irq(&tasklist_lock) |
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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
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