On Thu, 25 Oct 2007, Maxim Levitsky wrote: > Hi, > > Recently, trying to fix saa7134 suspend/resume problems I found that there > is a race between IRQ handler and .suspend , and that I cant let driver access the device > while its in D3 since it can lock up some systems. > > Now I am looking to fix those issues in two drivers that have my .suspend/.resume routines. > the saa7134 capture chip and dmfe, the davicom network driver. > > Looking through the dmfe code, I noticed yet another possible race. > A race between the .suspend, and a timer that serves both as a watchdog, and link state detector. > Again I need to prevent it from running during the suspend/resume, but how? > > I can use del_timer in .suspend, and mod_timer in .resume, but that doesn't protect against > race with already running timer. > I can use del_timer_sync, but it states that it is useless if timer re-enables itself, and I agree with that. > In dmfe case the timer does re-enable itself. That comment isn't right. del_timer_sync works perfectly well even if the timer routine re-enables itself, provided it stops doing so after a small number of iterations. > I can put checks in the timer for ->insuspend, and don't re enable it if set, > but that opens a new can of worms with memory barriers, etc... You don't have to worry about any of that stuff. Just check the insuspend flag and don't re-enable the timer if it is set. Even without any memory barriers, the timer routine won't iterate more than once or twice. Alan Stern _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
