Dne 11. 12. 20 v 17:59 Takashi Iwai napsal(a): > On Fri, 11 Dec 2020 17:45:45 +0100, > Jaroslav Kysela wrote: >> >> Dne 11. 12. 20 v 9:38 Takashi Iwai napsal(a): >>> Currently alsactl-restore tries to initialize the device when an error >>> is found for restore action. But this isn't the right behavior in the >>> case where the lock is held; it implies that another alsactl is >>> running concurrently, hence you shouldn't initialize the card at the >>> same time. The situation is found easily when two alsactls get >>> started by both udev and systemd (note that those two invocations are >>> the designed behavior, see /usr/lib/udev/rules.d/78-sound-cards.rules >>> for details). >>> >>> This patch changes load_state() not to handle the initialization if >>> the locking fails. >> >> The operation should serialize in this case (there's limit of 10 seconds which >> should be enough to finish the initialization). The state_lock() function >> should return -EBUSY when the file is locked (and I'm fine to change the >> behaviour from 'init' to 'skip' for this lock state). >> >> It seems that -EEXIST is returned when the lock file exists, but the >> open(file, O_CREAT|O_EXCL, 0644) caller has not enough priviledges to access >> this file when another user owns the file. >> >> But alsactl from /lib/udev/rules.d/90-alsa-restore.rules and >> /lib/systemd/system/alsa-restore.service should be run as root, right? > > Yes, it should be root. > > I also wondered how EEXIST comes, too. Maybe it's also the race > between the first open(O_RDWR) and the second > open(O_RDWR|O_CREAT|O_EXCL)? If so, it'd be better to go back again > to the normal open(O_RDWR)? Maybe. It seems enough to add EEXIST errno check to the "if (errno == EBUSY || errno == EAGAIN)" condition to repeat the open sequence. The -EBUSY will be returned correctly then. The one second delay is harmless in my eyes for the second task. Jaroslav -- Jaroslav Kysela <perex@xxxxxxxx> Linux Sound Maintainer; ALSA Project; Red Hat, Inc.
