kern/71509: sched_pin ignored by sched_4bsd

Stephan Uphoff ups at
Thu Sep 9 09:50:28 PDT 2004

The following reply was made to PR kern/71509; it has been noted by GNATS.

From: Stephan Uphoff <ups at>
To: FreeBSD-gnats-submit at, freebsd-bugs at
Subject: Re: kern/71509: sched_pin ignored by sched_4bsd
Date: Thu, 09 Sep 2004 12:46:55 -0400

 sched_pin() is used by the i386 pmap to optimize TLB invalidation in SMP
 systems by limiting it to a single processor.
 Ignoring the thread pin count can cause a thread to migrate to another
 CPU where obsolete cached TLB entries may point to the wrong physical
 page. This could for example cause pmap_copy_page to copy to/from the
 wrong page.

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