Date: Wed, 14 Feb 2007 23:23:16 +0300
From: Oleg Nesterov <oleg@tv-sign.ru>
To: Srivatsa Vaddagiri <vatsa@in.ibm.com>
Cc: Gautham R Shenoy <ego@in.ibm.com>, akpm@osdl.org, paulmck@us.ibm.com,
       mingo@elte.hu, dipankar@in.ibm.com, venkatesh.pallipadi@intel.com,
       linux-kernel@vger.kernel.org, rjw@sisk.pl
Subject: Re: [RFC PATCH(Experimental) 2/4] Revert changes to workqueue.c
Message-ID: <20070214202316.GD301@tv-sign.ru>
References: <20070214144031.GA15257@in.ibm.com> <20070214144229.GA19789@in.ibm.com> <20070214144305.GB19789@in.ibm.com> <20070214152458.GA5200@in.ibm.com>
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On 02/14, Srivatsa Vaddagiri wrote:
>
> On Wed, Feb 14, 2007 at 08:13:05PM +0530, Gautham R Shenoy wrote:
> > +	switch (action) {
> > +	case CPU_UP_PREPARE:
> > +		/* Create a new workqueue thread for it. */
> > +		list_for_each_entry(wq, &workqueues, list) {
> 
> Its probably safe to take the workqueue (spin) lock here (and other
> notifiers as well), before traversing the list.

We can't fork() under spin lock.

> 
> > +			cwq = per_cpu_ptr(wq->cpu_wq, hotcpu);
> > +			if (create_workqueue_thread(cwq, hotcpu)) {
> > +				printk("workqueue for %i failed\n", hotcpu);
> > +				return NOTIFY_BAD;
> > +			}
> > +		}
> > +		break;

Oleg.

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