On Sat, 10 Sep 2016, Peter Zijlstra wrote: > On Sat, Sep 10, 2016 at 09:16:59AM -0700, Christoph Hellwig wrote: > > On Thu, Sep 08, 2016 at 09:12:50AM -0700, Todd Kjos wrote: > > > In Android systems, the display pipeline relies on low > > > latency binder transactions and is therefore sensitive to > > > delays caused by contention for the global binder lock. > > > Jank is siginificantly reduced by disabling preemption > > > while the global binder lock is held. > > > > That's now how preempt_disable is supposed to use. It is for critical > > not, that's supposed to be _not_. Just to be absolutely clear, this is > NOT how you're supposed to use preempt_disable(). > > > sections that use per-cpu or similar resources. > > > > > > > > Originally-from: Riley Andrews <riandrews@xxxxxxxxxx> > > > Signed-off-by: Todd Kjos <tkjos@xxxxxxxxxx> > > > > @@ -389,7 +390,11 @@ static int task_get_unused_fd_flags(struct > > > binder_proc *proc, int flags) > > > rlim_cur = task_rlimit(proc->tsk, RLIMIT_NOFILE); > > > unlock_task_sighand(proc->tsk, &irqs); > > > > > > - return __alloc_fd(files, 0, rlim_cur, flags); > > > + preempt_enable_no_resched(); > > > + ret = __alloc_fd(files, 0, rlim_cur, flags); > > > + preempt_disable(); > > And the fact that people want to use preempt_enable_no_resched() shows > that they're absolutely clueless. > > This is so broken its not funny. > > NAK NAK NAK Indeed. Sprinkling random preempt_enabe/disable() pairs all over the place documents clearly that this is tinkering and not proper software engineering. NAK from my side as well. Thanks, Thomas _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
