On Tue, Dec 15, 2015 at 2:01 AM, Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxxxx> wrote: > Op 15-12-15 om 02:29 schreef Dmitry Torokhov: >> Userspace can close the sync device while there are still active fence >> points, in which case kernel produces the following warning: >> >> [ 43.853176] ------------[ cut here ]------------ >> [ 43.857834] WARNING: CPU: 0 PID: 892 at /mnt/host/source/src/third_party/kernel/v3.18/drivers/staging/android/sync.c:439 android_fence_release+0x88/0x104() >> [ 43.871741] CPU: 0 PID: 892 Comm: Binder_5 Tainted: G U 3.18.0-07661-g0550ce9 #1 >> [ 43.880176] Hardware name: Google Tegra210 Smaug Rev 1+ (DT) >> [ 43.885834] Call trace: >> [ 43.888294] [<ffffffc000207464>] dump_backtrace+0x0/0x10c >> [ 43.893697] [<ffffffc000207580>] show_stack+0x10/0x1c >> [ 43.898756] [<ffffffc000ab1258>] dump_stack+0x74/0xb8 >> [ 43.903814] [<ffffffc00021d414>] warn_slowpath_common+0x84/0xb0 >> [ 43.909736] [<ffffffc00021d530>] warn_slowpath_null+0x14/0x20 >> [ 43.915482] [<ffffffc00088aefc>] android_fence_release+0x84/0x104 >> [ 43.921582] [<ffffffc000671cc4>] fence_release+0x104/0x134 >> [ 43.927066] [<ffffffc00088b0cc>] sync_fence_free+0x74/0x9c >> [ 43.932552] [<ffffffc00088b128>] sync_fence_release+0x34/0x48 >> [ 43.938304] [<ffffffc000317bbc>] __fput+0x100/0x1b8 >> [ 43.943185] [<ffffffc000317cc8>] ____fput+0x8/0x14 >> [ 43.947982] [<ffffffc000237f38>] task_work_run+0xb0/0xe4 >> [ 43.953297] [<ffffffc000207074>] do_notify_resume+0x44/0x5c >> [ 43.958867] ---[ end trace 5a2aa4027cc5d171 ]--- >> >> Let's fix it by introducing a new optional callback (disable_signaling) >> to fence operations so that drivers can do proper clean ups when we >> remove last callback for given fence. >> >> Reviewed-by: Andrew Bresticker <abrestic@xxxxxxxxxxxx> >> Signed-off-by: Dmitry Torokhov <dtor@xxxxxxxxxxxx> >> > NACK! There's no way to do this race free. Can you please explain the race because as far as I can see there is not one. > The driver should hold a refcount until fence is signaled. If we are no longer interested in fence why do we need to wait for the fence to be signaled? Thanks. -- Dmitry _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
