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Message-ID: <20071017053754.GB9940@in.ibm.com> Date: Wed, 17 Oct 2007 11:07:54 +0530 From: Gautham R Shenoy <ego@...ibm.com> To: Rusty Russell <rusty@...tcorp.com.au> Cc: Linus Torvalds <torvalds@...ux-foundation.org>, Andrew Morton <akpm@...ux-foundation.org>, linux-kernel@...r.kernel.org, Srivatsa Vaddagiri <vatsa@...ibm.com>, Dipankar Sarma <dipankar@...ibm.com>, Oleg Nesterov <oleg@...sign.ru>, Ingo Molnar <mingo@...e.hu>, Paul E McKenney <paulmck@...ibm.com> Subject: Re: [RFC PATCH 1/4] Refcount Based Cpu-Hotplug Implementation On Wed, Oct 17, 2007 at 10:47:41AM +1000, Rusty Russell wrote: > On Tuesday 16 October 2007 20:34:17 Gautham R Shenoy wrote: > > This patch implements a Refcount + Waitqueue based model for > > cpu-hotplug. > > Hi Gautham, Hi Rusty, > > I can't see where you re-initialize the completion. The cpu_hotplug.readers_done is a global variable which has been initialized in cpu_hotplug_init. So I am wondering is the re-initialization required ? > > > +static void cpu_hotplug_begin(void) > > +{ > > + mutex_lock(&cpu_hotplug.lock); > > + cpu_hotplug.active_writer = current; > > + while (cpu_hotplug.refcount) { > > + mutex_unlock(&cpu_hotplug.lock); > > + wait_for_completion(&cpu_hotplug.readers_done); > > + mutex_lock(&cpu_hotplug.lock); > > + } > > AFAICT this will busy-wait on the second CPU hotplug. > Well when the first cpu_hotplug comes out of wait_for_completion, it would have decremented the ->done count, so it's as good as new for the second CPU hotplug, no? > Cheers, > Rusty. Thanks and Regards gautham. -- Gautham R Shenoy Linux Technology Center IBM India. "Freedom comes with a price tag of responsibility, which is still a bargain, because Freedom is priceless!" - 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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