Johannes Stezenbach wrote: > On Sat, May 13, 2006, Dyks, Axel (XL) wrote: > >>"cinergyt2_poll()" shouldn't return (POLLIN | POLLRDNORM | POLLPRI) when >>there are no pending events. User space programs that do non-bocking IO >>using "select()" and/or "poll()" would otherwise produce high system load. >>See http://forum.videolan.org/viewtopic.php?t=20529 for details. >> >>Signed-off-by: Axel Dyks <xl@xxxxxxxxxxxx> >> >>--- linux-2.6.16.orig/drivers/media/dvb/cinergyT2/cinergyT2.c 2006-03-20 06:53:29.000000000 +0100 >>+++ linux-2.6.16/drivers/media/dvb/cinergyT2/cinergyT2.c 2006-05-13 01:15:24.000000000 +0200 >>@@ -540,15 +540,18 @@ >> { >> struct dvb_device *dvbdev = file->private_data; >> struct cinergyt2 *cinergyt2 = dvbdev->priv; >>+ unsigned int mask = 0; >> >> if (cinergyt2->disconnect_pending || down_interruptible(&cinergyt2->sem)) >> return -ERESTARTSYS; >> >> poll_wait(file, &cinergyt2->poll_wq, wait); >> >>+ if (cinergyt2->pending_fe_events != 0) mask |= (POLLIN | POLLRDNORM | POLLPRI); > > > Please *never* do this. Better: > > if (cinergyt2->pending_fe_events != 0) > mask |= (POLLIN | POLLRDNORM | POLLPRI); No problem. Feel free to change the indention. Or shall I resend a modified version of the patch? >>+ >> up(&cinergyt2->sem); >> >>- return (POLLIN | POLLRDNORM | POLLPRI); >>+ return mask; >> } > > > > BTW, the sem stuff has been replaced by mutex. However, I wonder > why that sem/mutex is used at all. What data does it protect? > *cinergyt2 won't be released before the fd is closed (if it > would, cinergyt2->sem would also be invalid)... Yes, I've noted that someone has auto-converted the cinergyT2 module to use mutexes instead of semaphores (signed-off by Andrew Morton, I think). If needed, I can base by patch on the "mutexed" version. Shall I? BTW: Is this the correct place for contributing patches that meant to be integrated into the linux kernel sources? Regarding the semaphore: I think it "protects" the "wait queue" or rather the "pending-fe-events" value which may be asynchronly modified ... -- Axel _______________________________________________ linux-dvb@xxxxxxxxxxx http://www.linuxtv.org/cgi-bin/mailman/listinfo/linux-dvb
