why kernel implement "udelay" by cpu instructions?
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From: Rajat Jain on 4 Nov 2009 00:50 Hi, > > I thought hrtimers allow higher-precision wakeups these days? > Of course, if you only want to sleep for a few microseconds, the > context switch might take longer than you want to sleep... Yes, that is right. Sorry, I missed that. But that is purely HW dependent - if your HW providea a high precision timer (Such as HPET on latest Intel machines), that can be used for quicker sleeps. Thanks, Rajat -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: Rik van Riel on 4 Nov 2009 09:20
On 11/04/2009 12:36 AM, Bryan Donlan wrote: > I thought hrtimers allow higher-precision wakeups these days? > Of course, if you only want to sleep for a few microseconds, the > context switch might take longer than you want to sleep... Also, you may not be in a context where you can schedule. Sometimes drivers need to implement a small delay (to wait for something on the device) while holding a spinlock or while interrupts are disabled. -- All rights reversed. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |