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Subject: [Bug 193696] New: CAM AC_FOUND_DEVICE calls malloc(M_WAITOK) from
 THREAD_NO_SLEEPING() context
Date: Tue, 16 Sep 2014 21:50:19 +0000
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X-Bugzilla-Product: Base System
X-Bugzilla-Component: kern
X-Bugzilla-Version: 11.0-CURRENT
X-Bugzilla-Keywords: 
X-Bugzilla-Severity: Affects Some People
X-Bugzilla-Who: smferris@gmail.com
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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=193696

            Bug ID: 193696
           Summary: CAM AC_FOUND_DEVICE calls malloc(M_WAITOK) from
                    THREAD_NO_SLEEPING() context
           Product: Base System
           Version: 11.0-CURRENT
          Hardware: Any
                OS: Any
            Status: Needs Triage
          Severity: Affects Some People
          Priority: ---
         Component: kern
          Assignee: freebsd-bugs@FreeBSD.org
          Reporter: smferris@gmail.com

The CAM xpt_done_td is marked THREAD_NO_SLEEPING.  This is problematic since
the AC_FOUND_DEVICE async events still call functions such as disk_alloc() and
devstat_alloc() that malloc with M_WAITOK, so they could sleep, which panics
the
kernel.

You can spot the problem more easily by adding an ASSERT in malloc
that checks for M_WAITOK and THREAD_CAN_SLEEP, and then removing and
re-adding a device at run-time.  At least with mps, the initial device
creation works since it runs from dainit() in an intr config hook.

I'll attach a patch with the assertion that highlights the problem.

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