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Re: kern/39349: cpu affinity can make lwps non-schedulable

The following reply was made to PR kern/39349; it has been noted by GNATS.

From: (John Nemeth)
To: Jason Thorpe <>,
Subject: Re: kern/39349: cpu affinity can make lwps non-schedulable
Date: Thu, 14 Aug 2008 12:38:22 -0700

 On Jan 4,  5:14am, Jason Thorpe wrote:
 } On Aug 14, 2008, at 2:00 AM, wrote:
 } >> Number:         39349
 } >> Category:       kern
 } >> Synopsis:       cpu affinity can make lwps non-schedulable
 } >> State:          open
 } >> Description:
 } >    try:
 } >            # cpuctl offline 0
 } >            # cpuctl identify 0
 } >
 } >    "cpuctl identify" binds itself to cpu0, which is offline.
 } >    thus it will never be scheduled.  if it has a lock (eg. p->p_lock),
 } >    the entire system will hang soon.
 } Probably need to prevent binding to CPUs that have been taking  
 } offline.  But what to do about CPUs that already have bound threads  
      This looks like the obvious answer to me.
 } (which is all of them, of course).  Perhaps we need to make note when  
 } an LWP has taken a lock?
      I would like to see support for cpu hot swapping eventually.  This
 means that when a CPU is taken offline all bound threads and interrupts
 MUST be migrated.
 }-- End of excerpt from Jason Thorpe

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