Thanks for the reviews. We'll come up with a different solution. On Sat, Sep 10, 2016 at 10:28 AM, Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> wrote: > On Sat, Sep 10, 2016 at 06:37:29PM +0200, Thomas Gleixner wrote: >> 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. > > I have pointed out in the other thread for this patch (the one that had > a patch that could be applied) that the single lock in the binder code > is the main problem here, it should be solved instead of this messing > around with priorities. > > So don't worry, I'm not taking this change :) > > thanks, > > greg k-h _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
