On Fri, Mar 31, 2017 at 10:53:41AM -0700, Douglas Anderson wrote: > Sometimes when we're out of memory the OOM killer decides to kill a > process that's in binder_thread_read(). If we happen to be waiting > for work we'll get the kill signal and wake up. That's good. ...but > then we try to grab the binder lock before we return. That's bad. > > The problem is that someone else might be holding the one true global > binder lock. If that one other process is blocked then we can't > finish exiting. In the worst case, the other process might be blocked > waiting for memory. In that case we'll have a really hard time > exiting. > > On older kernels that don't have the OOM reaper (or something > similar), like kernel 4.4, this is a really big problem and we end up > with a simple deadlock because: > * Once we pick a process to OOM kill we won't pick another--we first > wait for the process we picked to die. The reasoning is that we've > given the doomed process access to special memory pools so it can > quit quickly and we don't have special pool memory to go around. > * We don't have any type of "special access donation" that would give > the mutex holder our special access. > > On kernel 4.4 w/ binder patches, we easily see this happen: <snip> How does your change interact with the recent "break up the binder big lock" patchset: https://android-review.googlesource.com/#/c/354698/ Have you tried that series out to see if it helps out any? thanks, greg k-h _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
