>> With strace, when running 500 concurrent mem-hog tasks on the same >> kernel, 33 of them failed with: >> >> strace: ../sysdeps/nptl/fork.c:136: __libc_fork: Assertion >> `THREAD_GETMEM (self, tid) != ppid' failed. >> >> Which is: https://sourceware.org/bugzilla/show_bug.cgi?id=15392 >> And discussed before at: https://lkml.org/lkml/2015/2/6/470 but that >> patch was not accepted. > > OK, so the problem is that the oom killed task doesn't report the futex > release properly? If yes then I fail to see how that is memcg specific. > Could you try to clarify what you consider a bug again, please? I am not > really sure I understand this report. It looks like it is just a very easy way to reproduce the problem that Konstantin described in that lkml thread. That patch was not accepted and I see no other fixes for that issue upstream. Here is a copy of his root-cause analysis from said thread: Whole sequence looks like: task calls fork, glibc calls syscall clone with CLONE_CHILD_SETTID and passes pointer to TLS THREAD_SELF->tid as argument. Child task gets read-only copy of VM including TLS. Child calls put_user() to handle CLONE_CHILD_SETTID from schedule_tail(). put_user() trigger page fault and it fails because do_wp_page() hits memcg limit without invoking OOM-killer because this is page-fault from kernel-space. Put_user returns -EFAULT, which is ignored. Child returns into user-space and catches here assert (THREAD_GETMEM (self, tid) != ppid), glibc tries to print something but hangs on deadlock on internal locks. Halt and catch fire. Regards -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>