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Message-ID: <20070131110722.GA1847@elte.hu> Date: Wed, 31 Jan 2007 12:07:23 +0100 From: Ingo Molnar <mingo@...e.hu> To: Daniel Walker <dwalker@...sta.com> Cc: akpm@...l.org, linux-kernel@...r.kernel.org, johnstul@...ibm.com Subject: Re: [PATCH 11/23] clocksource: atomic signals * Daniel Walker <dwalker@...sta.com> wrote: > Modifies the way clocks are switched to in the timekeeping code. The > original code would constantly monitor the clocksource list checking > for newly added clocksources. I modified this by using atomic types to > signal when a new clock is added. This allows the operation to be used > only when it's needed. I see little difference between your and John's code: both poll something - you poll an atomic "did a new clocksource arrive" flag in the timer interrupt, John takes the clocksource_lock spinlock and checks a "did a new clocksource arrive" variable. Both are global atomic variables in essence. what i'd see as a real cleanup here would be to get away from this 'poll whether there's any clocksource update' model, and to just ensure that a running timer irq will always see the latest clocksource. I.e. to run the change_clocksource() logic (and the following updates) when a new clock source is selected - not when the next timer interrupt runs. That would propagate all effects of a new clock source immediately. Ingo - 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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