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Message-Id: <200710250612.44296.maximlevitsky@gmail.com> Date: Thu, 25 Oct 2007 06:12:44 +0200 From: Maxim Levitsky <maximlevitsky@...il.com> To: linux-kernel@...r.kernel.org Cc: linux-pm@...ts.linux-foundation.org, netdev@...r.kernel.org Subject: QUESTION: How to fix race between .suspend routine and watchdog timer 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. 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... So please tell me how properly to do that. By the way, this problem, together with synchronize_irq it very generic, since most drivers have and irq handler, and a timeout timer. Best regards, Maxim Levitsky - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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