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Date: Mon, 27 Aug 2007 20:25:16 +0400 From: Oleg Nesterov <oleg@...sign.ru> To: Cliff Wickman <cpw@....com> Cc: akpm@...ux-foundation.org, ego@...ibm.com, mingo@...e.hu, vatsa@...ibm.com, pj@....com, linux-kernel@...r.kernel.org Subject: Re: [PATCH 1/1] V3: hotplug cpu: migrate a task within its cpuset On 08/27, Cliff Wickman wrote: > > --- linus.070821.orig/kernel/sched.c > +++ linus.070821/kernel/sched.c > @@ -61,6 +61,7 @@ > #include <linux/delayacct.h> > #include <linux/reciprocal_div.h> > #include <linux/unistd.h> > +#include <linux/cpuset.h> > > #include <asm/tlb.h> > > @@ -5091,6 +5092,19 @@ restart: > if (dest_cpu == NR_CPUS) > dest_cpu = any_online_cpu(p->cpus_allowed); > > + /* try to stay on the same cpuset */ > + if (dest_cpu == NR_CPUS) { > + rq = task_rq_lock(p, &flags); > + /* > + * The cpuset_cpus_allowed_locked() variant of > + * cpuset_cpus_allowed() will not block > + * It must be called within calls to cpuset_lock/cpuset_unlock. > + */ > + p->cpus_allowed = cpuset_cpus_allowed_locked(p); > + dest_cpu = any_online_cpu(p->cpus_allowed); > + task_rq_unlock(rq, &flags); No, no, we can't take task_lock() under rq->lock, nesting error. I think we need a local "cpumask_t cpus_allowed = cpuset_cpus_allowed_locked()", like sched_setaffinity() does. task_lock() doesn't disable irqs, this means that it can't be used under any lock which can be used from interrupt context. Oleg. - 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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