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Subject: [Bug 192926] New: [patch] sched_yield is a no-op
Date: Fri, 22 Aug 2014 18:24:00 +0000
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X-Bugzilla-Product: Base System
X-Bugzilla-Component: kern
X-Bugzilla-Version: 10.0-RELEASE
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X-Bugzilla-Severity: Affects Some People
X-Bugzilla-Who: eric@vangyzen.net
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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=192926

            Bug ID: 192926
           Summary: [patch] sched_yield is a no-op
           Product: Base System
           Version: 10.0-RELEASE
          Hardware: Any
                OS: Any
            Status: Needs Triage
          Severity: Affects Some People
          Priority: ---
         Component: kern
          Assignee: freebsd-bugs@FreeBSD.org
          Reporter: eric@vangyzen.net

Created attachment 146161
  --> https://bugs.freebsd.org/bugzilla/attachment.cgi?id=146161&action=edit
proposed patch

sched_yield() is a no-op.  The thread is put back on the CPU immediately,
preventing other threads from running.  ru_nvcsw gets incremented, but ktrace
does not show a context switch.

This was introduced by r239157:

    http://svnweb.freebsd.org/base?view=revision&revision=r239157

I found this on 10.0-RELEASE-p7, but the same code exists in head.

I will attach a test case and patch against releng/10.0.

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