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  1. 18 Apr, 2017 1 commit
    • Mika Kuoppala's avatar
      drm/i915: Avoid tweaking evaluation thresholds on Baytrail v3 · cb0a2cba
      Mika Kuoppala authored 
      commit 34dc8993 upstream.

Certain Baytrails, namely the 4 cpu core variants, have been
plaqued by spurious system hangs, mostly occurring with light loads.

Multiple bisects by various people point to a commit which changes the
reclocking strategy for Baytrail to follow its bigger brethen:
commit 8fb55197 ("drm/i915: Agressive downclocking on Baytrail")

There is also a review comment attached to this commit from Deepak S
on avoiding punit access on Cherryview and thus it was excluded on
common reclocking path. By taking the same approach and omitting
the punit access by not tweaking the thresholds when the hardware
has been asked to move into different frequency, considerable gains
in stability have been observed.

With J1900 box, light render/video load would end up in system hang
in usually less than 12 hours. With this patch applied, the cumulative
uptime has now been 34 days without issues. To provoke system hang,
light loads on both render and bsd engines in parallel have been used:
glxgears >/dev/null 2>/dev/null &
mpv --vo=vaapi --hwdec=vaapi --loop=inf vid.mp4

So far, author has not witnessed system hang with above load
and this patch applied. Reports from the tenacious people at
kernel bugzilla are also promising.

Considering that the punit access frequency with this patch is
considerably less, there is a possibility that this will push
the, still unknown, root cause past the triggering point on most loads.

But as we now can reliably reproduce the hang independently,
we can reduce the pain that users are having and use a
static thresholds until a root cause is found.

v3: don't break debugfs and simplification (Chris Wilson)

References: https://bugzilla.kernel.org/show_bug.cgi?id=109051
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Len Brown <len.brown@intel.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Jani Nikula <jani.nikula@intel.com>
Cc: fritsch@xbmc.org
Cc: miku@iki.fi
Cc: Ezequiel Garcia <ezequiel@vanguardiasur.com.ar>
CC: Michal Feix <michal@feix.cz>
Cc: Hans de Goede <hdegoede@redhat.com>
Cc: Deepak S <deepak.s@linux.intel.com>
Cc: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Acked-by: default avatarDaniel Vetter <daniel.vetter@ffwll.ch>
Acked-by: default avatarChris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: default avatarMika Kuoppala <mika.kuoppala@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1487166779-26945-1-git-send-email-mika.kuoppala@intel.com
(cherry picked from commit 6067a27d)
Signed-off-by: default avatarJani Nikula <jani.nikula@intel.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
      cb0a2cba
  3. 12 Apr, 2017 33 commits
  5. 08 Apr, 2017 6 commits
    • Greg Kroah-Hartman's avatar
      Linux 4.4.60 · 8f8ee970
      Greg Kroah-Hartman authored
      8f8ee970
    • Jason A. Donenfeld's avatar
      padata: avoid race in reordering · 84bd21a7
      Jason A. Donenfeld authored 
      commit de5540d0 upstream.

Under extremely heavy uses of padata, crashes occur, and with list
debugging turned on, this happens instead:

[87487.298728] WARNING: CPU: 1 PID: 882 at lib/list_debug.c:33
__list_add+0xae/0x130
[87487.301868] list_add corruption. prev->next should be next
(ffffb17abfc043d0), but was ffff8dba70872c80. (prev=ffff8dba70872b00).
[87487.339011]  [<ffffffff9a53d075>] dump_stack+0x68/0xa3
[87487.342198]  [<ffffffff99e119a1>] ? console_unlock+0x281/0x6d0
[87487.345364]  [<ffffffff99d6b91f>] __warn+0xff/0x140
[87487.348513]  [<ffffffff99d6b9aa>] warn_slowpath_fmt+0x4a/0x50
[87487.351659]  [<ffffffff9a58b5de>] __list_add+0xae/0x130
[87487.354772]  [<ffffffff9add5094>] ? _raw_spin_lock+0x64/0x70
[87487.357915]  [<ffffffff99eefd66>] padata_reorder+0x1e6/0x420
[87487.361084]  [<ffffffff99ef0055>] padata_do_serial+0xa5/0x120

padata_reorder calls list_add_tail with the list to which its adding
locked, which seems correct:

spin_lock(&squeue->serial.lock);
list_add_tail(&padata->list, &squeue->serial.list);
spin_unlock(&squeue->serial.lock);

This therefore leaves only place where such inconsistency could occur:
if padata->list is added at the same time on two different threads.
This pdata pointer comes from the function call to
padata_get_next(pd), which has in it the following block:

next_queue = per_cpu_ptr(pd->pqueue, cpu);
padata = NULL;
reorder = &next_queue->reorder;
if (!list_empty(&reorder->list)) {
       padata = list_entry(reorder->list.next,
                           struct padata_priv, list);
       spin_lock(&reorder->lock);
       list_del_init(&padata->list);
       atomic_dec(&pd->reorder_objects);
       spin_unlock(&reorder->lock);

       pd->processed++;

       goto out;
}
out:
return padata;

I strongly suspect that the problem here is that two threads can race
on reorder list. Even though the deletion is locked, call to
list_entry is not locked, which means it's feasible that two threads
pick up the same padata object and subsequently call list_add_tail on
them at the same time. The fix is thus be hoist that lock outside of
that block.
Signed-off-by: default avatarJason A. Donenfeld <Jason@zx2c4.com>
Acked-by: default avatarSteffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: default avatarHerbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
      84bd21a7
    • NeilBrown's avatar
      blk: Ensure users for current->bio_list can see the full list. · 5cca175b
      NeilBrown authored 
      commit f5fe1b51 upstream.

Commit 79bd9959 ("blk: improve order of bio handling in generic_make_request()")
changed current->bio_list so that it did not contain *all* of the
queued bios, but only those submitted by the currently running
make_request_fn.

There are two places which walk the list and requeue selected bios,
and others that check if the list is empty.  These are no longer
correct.

So redefine current->bio_list to point to an array of two lists, which
contain all queued bios, and adjust various code to test or walk both
lists.
Signed-off-by: default avatarNeilBrown <neilb@suse.com>
Fixes: 79bd9959 ("blk: improve order of bio handling in generic_make_request()")
Signed-off-by: default avatarJens Axboe <axboe@fb.com>
[jwang: backport to 4.4]
Signed-off-by: default avatarJack Wang <jinpu.wang@profitbricks.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
[bwh: Restore changes in device-mapper from upstream version]
Signed-off-by: default avatarBen Hutchings <ben.hutchings@codethink.co.uk>
      5cca175b
    • NeilBrown's avatar
      blk: improve order of bio handling in generic_make_request() · 2cbd78f4
      NeilBrown authored 
      commit 79bd9959 upstream.

To avoid recursion on the kernel stack when stacked block devices
are in use, generic_make_request() will, when called recursively,
queue new requests for later handling.  They will be handled when the
make_request_fn for the current bio completes.

If any bios are submitted by a make_request_fn, these will ultimately
be handled seqeuntially.  If the handling of one of those generates
further requests, they will be added to the end of the queue.

This strict first-in-first-out behaviour can lead to deadlocks in
various ways, normally because a request might need to wait for a
previous request to the same device to complete.  This can happen when
they share a mempool, and can happen due to interdependencies
particular to the device.  Both md and dm have examples where this happens.

These deadlocks can be erradicated by more selective ordering of bios.
Specifically by handling them in depth-first order.  That is: when the
handling of one bio generates one or more further bios, they are
handled immediately after the parent, before any siblings of the
parent.  That way, when generic_make_request() calls make_request_fn
for some particular device, we can be certain that all previously
submited requests for that device have been completely handled and are
not waiting for anything in the queue of requests maintained in
generic_make_request().

An easy way to achieve this would be to use a last-in-first-out stack
instead of a queue.  However this will change the order of consecutive
bios submitted by a make_request_fn, which could have unexpected consequences.
Instead we take a slightly more complex approach.
A fresh queue is created for each call to a make_request_fn.  After it completes,
any bios for a different device are placed on the front of the main queue, followed
by any bios for the same device, followed by all bios that were already on
the queue before the make_request_fn was called.
This provides the depth-first approach without reordering bios on the same level.

This, by itself, it not enough to remove all deadlocks.  It just makes
it possible for drivers to take the extra step required themselves.

To avoid deadlocks, drivers must never risk waiting for a request
after submitting one to generic_make_request.  This includes never
allocing from a mempool twice in the one call to a make_request_fn.

A common pattern in drivers is to call bio_split() in a loop, handling
the first part and then looping around to possibly split the next part.
Instead, a driver that finds it needs to split a bio should queue
(with generic_make_request) the second part, handle the first part,
and then return.  The new code in generic_make_request will ensure the
requests to underlying bios are processed first, then the second bio
that was split off.  If it splits again, the same process happens.  In
each case one bio will be completely handled before the next one is attempted.

With this is place, it should be possible to disable the
punt_bios_to_recover() recovery thread for many block devices, and
eventually it may be possible to remove it completely.

Ref: http://www.spinics.net/lists/raid/msg54680.htmlTested-by: default avatarJinpu Wang <jinpu.wang@profitbricks.com>
Inspired-by: default avatarLars Ellenberg <lars.ellenberg@linbit.com>
Signed-off-by: default avatarNeilBrown <neilb@suse.com>
Signed-off-by: default avatarJens Axboe <axboe@fb.com>
[jwang: backport to 4.4]
Signed-off-by: default avatarJack Wang <jinpu.wang@profitbricks.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
      2cbd78f4
    • Alexandre Belloni's avatar
      power: reset: at91-poweroff: timely shutdown LPDDR memories · 063d30f1
      Alexandre Belloni authored 
      commit 0b040874 upstream.

LPDDR memories can only handle up to 400 uncontrolled power off. Ensure the
proper power off sequence is used before shutting down the platform.
Signed-off-by: default avatarAlexandre Belloni <alexandre.belloni@free-electrons.com>
Signed-off-by: default avatarSebastian Reichel <sre@kernel.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
      063d30f1
    • David Hildenbrand's avatar
      KVM: kvm_io_bus_unregister_dev() should never fail · 42462d23
      David Hildenbrand authored 
      commit 90db1043 upstream.

No caller currently checks the return value of
kvm_io_bus_unregister_dev(). This is evil, as all callers silently go on
freeing their device. A stale reference will remain in the io_bus,
getting at least used again, when the iobus gets teared down on
kvm_destroy_vm() - leading to use after free errors.

There is nothing the callers could do, except retrying over and over
again.

So let's simply remove the bus altogether, print an error and make
sure no one can access this broken bus again (returning -ENOMEM on any
attempt to access it).

Fixes: e93f8a0f ("KVM: convert io_bus to SRCU")
Reported-by: default avatarDmitry Vyukov <dvyukov@google.com>
Reviewed-by: default avatarCornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: default avatarDavid Hildenbrand <david@redhat.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
      42462d23
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