perf-buildid-cache(1)
=====================

NAME
----
perf-buildid-cache - Manage build-id cache.

SYNOPSIS
--------
[verse]
'perf buildid-cache <options>'

DESCRIPTION
-----------
This command manages the build-id cache. It can add, remove, update and purge
files to/from the cache. In the future it should as well set upper limits for
the space used by the cache, etc.
This also scans the target binary for SDT (Statically Defined Tracing) and
record it along with the buildid-cache, which will be used by perf-probe.
For more details, see linkperf:perf-probe[1].

OPTIONS
-------
-a::
--add=::
        Add specified file to the cache.
-k::
--kcore::
        Add specified kcore file to the cache. For the current host that is
        /proc/kcore which requires root permissions to read. Be aware that
        running 'perf buildid-cache' as root may update root's build-id cache
        not the user's. Use the -v option to see where the file is created.
        Note that the copied file contains only code sections not the whole core
        image. Note also that files "kallsyms" and "modules" must also be in the
        same directory and are also copied.  All 3 files are created with read
        permissions for root only. kcore will not be added if there is already a
        kcore in the cache (with the same build-id) that has the same modules at
        the same addresses. Use the -v option to see if a copy of kcore is
        actually made.
-r::
--remove=::
        Remove a cached binary which has same build-id of specified file
        from the cache.
-p::
--purge=::
        Purge all cached binaries including older caches which have specified
	path from the cache.
-M::
--missing=::
	List missing build ids in the cache for the specified file.
-u::
--update=::
	Update specified file of the cache. Note that this doesn't remove
	older entires since those may be still needed for annotating old
	(or remote) perf.data. Only if there is already a cache which has
	exactly same build-id, that is replaced by new one. It can be used
	to update kallsyms and kernel dso to vmlinux in order to support
	annotation.

-v::
--verbose::
	Be more verbose.

SEE ALSO
--------
linkperf:perf-record[1], linkperf:perf-report[1], linkperf:perf-buildid-list[1]
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<div class='path'>path: <a href='/cgit.cgi/linux/net-next.git/commit/?id=39cb2c9a316e77f6dfba96c543e55b6672d5a37e'>root</a>/<a href='/cgit.cgi/linux/net-next.git/commit/sound?id=39cb2c9a316e77f6dfba96c543e55b6672d5a37e'>sound</a>/<a href='/cgit.cgi/linux/net-next.git/commit/sound/pcmcia?id=39cb2c9a316e77f6dfba96c543e55b6672d5a37e'>pcmcia</a>/<a href='/cgit.cgi/linux/net-next.git/commit/sound/pcmcia/vx?id=39cb2c9a316e77f6dfba96c543e55b6672d5a37e'>vx</a>/<a href='/cgit.cgi/linux/net-next.git/commit/sound/pcmcia/vx/vxp_mixer.c?id=39cb2c9a316e77f6dfba96c543e55b6672d5a37e'>vxp_mixer.c</a></div><div class='content'><div class='cgit-panel'><b>diff options</b><form method='get'><input type='hidden' name='id' value='39cb2c9a316e77f6dfba96c543e55b6672d5a37e'/><table><tr><td colspan='2'/></tr><tr><td class='label'>context:</td><td class='ctrl'><select name='context' onchange='this.form.submit();'><option value='1'>1</option><option value='2'>2</option><option value='3' selected='selected'>3</option><option value='4'>4</option><option value='5'>5</option><option value='6'>6</option><option value='7'>7</option><option value='8'>8</option><option value='9'>9</option><option value='10'>10</option><option value='15'>15</option><option value='20'>20</option><option value='25'>25</option><option value='30'>30</option><option value='35'>35</option><option value='40'>40</option></select></td></tr><tr><td class='label'>space:</td><td class='ctrl'><select name='ignorews' onchange='this.form.submit();'><option value='0' selected='selected'>include</option><option value='1'>ignore</option></select></td></tr><tr><td class='label'>mode:</td><td class='ctrl'><select name='dt' onchange='this.form.submit();'><option value='0' selected='selected'>unified</option><option value='1'>ssdiff</option><option value='2'>stat only</option></select></td></tr><tr><td/><td class='ctrl'><noscript><input type='submit' value='reload'/></noscript></td></tr></table></form></div><table summary='commit info' class='commit-info'>
<tr><th>author</th><td>Linus Torvalds &lt;torvalds@linux-foundation.org&gt;</td><td class='right'>2017-01-29 13:50:06 -0800</td></tr>
<tr><th>committer</th><td>Linus Torvalds &lt;torvalds@linux-foundation.org&gt;</td><td class='right'>2017-01-29 13:50:06 -0800</td></tr>
<tr><th>commit</th><td colspan='2' class='oid'><a href='/cgit.cgi/linux/net-next.git/commit/sound/pcmcia/vx/vxp_mixer.c?id=39cb2c9a316e77f6dfba96c543e55b6672d5a37e'>39cb2c9a316e77f6dfba96c543e55b6672d5a37e</a> (<a href='/cgit.cgi/linux/net-next.git/patch/sound/pcmcia/vx/vxp_mixer.c?id=39cb2c9a316e77f6dfba96c543e55b6672d5a37e'>patch</a>)</td></tr>
<tr><th>tree</th><td colspan='2' class='oid'><a href='/cgit.cgi/linux/net-next.git/tree/?id=39cb2c9a316e77f6dfba96c543e55b6672d5a37e'>98fe974ee4e20121253de7f61fc8d01bdb3821c1</a> /<a href='/cgit.cgi/linux/net-next.git/tree/sound/pcmcia/vx/vxp_mixer.c?id=39cb2c9a316e77f6dfba96c543e55b6672d5a37e'>sound/pcmcia/vx/vxp_mixer.c</a></td></tr>
<tr><th>parent</th><td colspan='2' class='oid'><a href='/cgit.cgi/linux/net-next.git/commit/sound/pcmcia/vx/vxp_mixer.c?id=2c5d9555d6d937966d79d4c6529a5f7b9206e405'>2c5d9555d6d937966d79d4c6529a5f7b9206e405</a> (<a href='/cgit.cgi/linux/net-next.git/diff/sound/pcmcia/vx/vxp_mixer.c?id=39cb2c9a316e77f6dfba96c543e55b6672d5a37e&amp;id2=2c5d9555d6d937966d79d4c6529a5f7b9206e405'>diff</a>)</td></tr></table>
<div class='commit-subject'>drm/i915: Check for NULL i915_vma in intel_unpin_fb_obj()</div><div class='commit-msg'>I've seen this trigger twice now, where the i915_gem_object_to_ggtt()
call in intel_unpin_fb_obj() returns NULL, resulting in an oops
immediately afterwards as the (inlined) call to i915_vma_unpin_fence()
tries to dereference it.

It seems to be some race condition where the object is going away at
shutdown time, since both times happened when shutting down the X
server.  The call chains were different:

 - VT ioctl(KDSETMODE, KD_TEXT):

    intel_cleanup_plane_fb+0x5b/0xa0 [i915]
    drm_atomic_helper_cleanup_planes+0x6f/0x90 [drm_kms_helper]
    intel_atomic_commit_tail+0x749/0xfe0 [i915]
    intel_atomic_commit+0x3cb/0x4f0 [i915]
    drm_atomic_commit+0x4b/0x50 [drm]
    restore_fbdev_mode+0x14c/0x2a0 [drm_kms_helper]
    drm_fb_helper_restore_fbdev_mode_unlocked+0x34/0x80 [drm_kms_helper]
    drm_fb_helper_set_par+0x2d/0x60 [drm_kms_helper]
    intel_fbdev_set_par+0x18/0x70 [i915]
    fb_set_var+0x236/0x460
    fbcon_blank+0x30f/0x350
    do_unblank_screen+0xd2/0x1a0
    vt_ioctl+0x507/0x12a0
    tty_ioctl+0x355/0xc30
    do_vfs_ioctl+0xa3/0x5e0
    SyS_ioctl+0x79/0x90
    entry_SYSCALL_64_fastpath+0x13/0x94

 - i915 unpin_work workqueue:

    intel_unpin_work_fn+0x58/0x140 [i915]
    process_one_work+0x1f1/0x480
    worker_thread+0x48/0x4d0
    kthread+0x101/0x140

and this patch purely papers over the issue by adding a NULL pointer
check and a WARN_ON_ONCE() to avoid the oops that would then generally
make the machine unresponsive.

Other callers of i915_gem_object_to_ggtt() seem to also check for the
returned pointer being NULL and warn about it, so this clearly has
happened before in other places.

[ Reported it originally to the i915 developers on Jan 8, applying the
  ugly workaround on my own now after triggering the problem for the
  second time with no feedback.

  This is likely to be the same bug reported as

     https://bugs.freedesktop.org/show_bug.cgi?id=98829
     https://bugs.freedesktop.org/show_bug.cgi?id=99134

  which has a patch for the underlying problem, but it hasn't gotten to
  me, so I'm applying the workaround. ]

Cc: Daniel Vetter &lt;daniel.vetter@intel.com&gt;
Cc: Jani Nikula &lt;jani.nikula@linux.intel.com&gt;
Cc: Ville Syrjälä &lt;ville.syrjala@linux.intel.com&gt;
Cc: Chris Wilson &lt;chris@chris-wilson.co.uk&gt;
Cc: Maarten Lankhorst &lt;maarten.lankhorst@linux.intel.com&gt;
Cc: Tvrtko Ursulin &lt;tvrtko.ursulin@intel.com&gt;
Cc: Imre Deak &lt;imre.deak@intel.com&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</div><div class='diffstat-header'><a href='/cgit.cgi/linux/net-next.git/diff/?id=39cb2c9a316e77f6dfba96c543e55b6672d5a37e'>Diffstat</a> (limited to 'sound/pcmcia/vx/vxp_mixer.c')</div><table summary='diffstat' class='diffstat'>