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  1. 24 Jul, 2006 8 commits
  3. 23 Jul, 2006 5 commits
    • Roland Dreier's avatar
      IB/uverbs: Fix lockdep warnings · 43db2bc0
      Roland Dreier authored 
      Lockdep warns because uverbs is trying to take uobj->mutex when it
already holds that lock.  This is because there are really multiple
types of uobjs even though all of their locks are initialized in
common code.
Signed-off-by: default avatarRoland Dreier <rolandd@cisco.com>
      43db2bc0
    • Michael S. Tsirkin's avatar
      IB/uverbs: Fix unlocking in error paths · ec924b47
      Michael S. Tsirkin authored 
      ib_uverbs_create_ah() and ib_uverbs_create_srq() did not release the
PD's read lock in their error paths, which lead to deadlock when
destroying the PD.
Signed-off-by: default avatarMichael S. Tsirkin <mst@mellanox.co.il>
Signed-off-by: default avatarRoland Dreier <rolandd@cisco.com>
      ec924b47
    • Paul Jackson's avatar
      [PATCH] Cpuset: fix ABBA deadlock with cpu hotplug lock · abb5a5cc
      Paul Jackson authored 
      Fix ABBA deadlock between lock_cpu_hotplug() and the cpuset
callback_mutex lock.

It only happens on cpu_exclusive cpusets, due to the dynamic
sched domain code trying to take the cpu hotplug lock inside
the cpuset callback_mutex lock.

This bug has apparently been here for several months, but didn't
get hit until the right customer load on a large system.

This fix appears right from inspection, but it will take a few
more days running it on that customers workload to be confident
we nailed it.  We don't have any other reproducible test case.

The cpu_hotplug_lock() tends to cover large runs of code.
The other places that hold both that lock and the cpuset callback
mutex lock always nest the cpuset lock inside the hotplug lock.
This place tries to do the reverse, risking an ABBA deadlock.

This is in the cpuset_rmdir() code, where we:
  * take the callback_mutex lock
  * mark the cpuset CS_REMOVED
  * call update_cpu_domains for cpu_exclusive cpusets
  * in that call, take the cpu_hotplug lock if the
    cpuset is marked for removal.

Thanks to Jack Steiner for identifying this deadlock.

The fix is to tear down the dynamic sched domain before we grab
the cpuset callback_mutex lock.  This way, the two locks are
serialized, with the hotplug lock taken and released before
trying for the cpuset lock.

I suspect that this bug was introduced when I changed the
cpuset locking from one lock to two.  The dynamic sched domain
dependency on cpu_exclusive cpusets and its hotplug hooks were
added to this code earlier, when cpusets had only a single lock.
It may well have been fine then.
Signed-off-by: default avatarPaul Jackson <pj@sgi.com>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
      abb5a5cc
    • Linus Torvalds's avatar
      cpu hotplug: simplify and hopefully fix locking · aa953877
      Linus Torvalds authored 
      The CPU hotplug locking was quite messy, with a recursive lock to
handle the fact that both the actual up/down sequence wanted to
protect itself from being re-entered, but the callbacks that it
called also tended to want to protect themselves from CPU events.

This splits the lock into two (one to serialize the whole hotplug
sequence, the other to protect against the CPU present bitmaps
changing). The latter still allows recursive usage because some
subsystems (ondemand policy for cpufreq at least) had already gotten
too used to the lax locking, but the locking mistakes are hopefully
now less fundamental, and we now warn about recursive lock usage
when we see it, in the hope that it can be fixed.
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
      aa953877
    • Linus Torvalds's avatar
      [cpufreq] ondemand: make shutdown sequence more robust · 2cd7cbdf
      Linus Torvalds authored 
      Shutting down the ondemand policy was fraught with potential
problems, causing issues for SMP suspend (which wants to hot-
unplug) all but the last CPU.

This should fix at least the worst problems (divide-by-zero
and infinite wait for the workqueue to shut down).
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
      2cd7cbdf
  5. 21 Jul, 2006 27 commits