Commit Graph

21 Commits

Author SHA1 Message Date
Stefan Hajnoczi 1faa5bb732 thread-pool: clean up thread_pool_completion_bh()
This patch simplifies thread_pool_completion_bh().

The function first checks elem->state:

  if (elem->state != THREAD_DONE) {
      continue;
  }

It then goes on to check elem->state == THREAD_DONE although we already
know this must be the case.

The QLIST_REMOVE() is duplicated down both branches of an if-else
statement so that can be lifted out as well.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Message-id: 1427992762-10126-1-git-send-email-stefanha@redhat.com
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2015-04-28 15:36:09 +02:00
Markus Armbruster 097310b53e block: Rename BlockDriverCompletionFunc to BlockCompletionFunc
I'll use it with block backends shortly, and the name is going to fit
badly there.  It's a block layer thing anyway, not just a block driver
thing.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2014-10-20 13:41:27 +02:00
Markus Armbruster 7c84b1b831 block: Rename BlockDriverAIOCB* to BlockAIOCB*
I'll use BlockDriverAIOCB with block backends shortly, and the name is
going to fit badly there.  It's a block layer thing anyway, not just a
block driver thing.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2014-10-20 13:41:27 +02:00
Fam Zheng 8007429a99 block: Rename qemu_aio_release -> qemu_aio_unref
Suggested-by: Benoît Canet <benoit.canet@irqsave.net>
Signed-off-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2014-09-22 11:39:17 +01:00
Fam Zheng 3391f5e51c thread-pool: Convert thread_pool_aiocb_info.cancel to cancel_async
The .cancel_async shares the same the first half with .cancel: try to
steal the request if not submitted yet. In this case set the elem to
THREAD_DONE status and ret to -ECANCELED, which means
thread_pool_completion_bh will call the cb with -ECANCELED.

If the request is already submitted, do nothing, as we know the normal
completion will happen in the future.

Testing code update:

Before, done_cb is only called if the request is already submitted by
thread pool. Now done_cb is always called, even before it is submitted,
because we emulate bdrv_aio_cancel with bdrv_aio_cancel_async. So also
update the test criteria accordingly.

Signed-off-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2014-09-22 11:39:02 +01:00
Markus Armbruster a31e69cf00 thread-pool: Drop unnecessary includes
Dragging block_int.h into a header is *not* nice.  Fortunately, this
is the only offender.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2014-09-10 10:41:29 +02:00
Stefan Hajnoczi 3c80ca158c thread-pool: avoid deadlock in nested aio_poll() calls
The thread pool has a race condition if two elements complete before
thread_pool_completion_bh() runs:

  If element A's callback waits for element B using aio_poll() it will
  deadlock since pool->completion_bh is not marked scheduled when the
  nested aio_poll() runs.

Fix this by marking the BH scheduled while thread_pool_completion_bh()
is executing.  This way any nested aio_poll() loops will enter
thread_pool_completion_bh() and complete the remaining elements.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2014-08-15 15:07:14 +02:00
Stefan Hajnoczi c2e50e3d11 thread-pool: avoid per-thread-pool EventNotifier
EventNotifier is implemented using an eventfd or pipe.  It therefore
consumes file descriptors, which can be limited by rlimits and should
therefore be used sparingly.

Switch from EventNotifier to QEMUBH in thread-pool.c.  Originally
EventNotifier was used because qemu_bh_schedule() was not thread-safe
yet.

Reported-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2014-08-15 15:07:14 +02:00
Fam Zheng 271c0f68b4 aio: Fix use-after-free in cancellation path
The current flow of canceling a thread from THREAD_ACTIVE state is:

  1) Caller wants to cancel a request, so it calls thread_pool_cancel.

  2) thread_pool_cancel waits on the conditional variable
     elem->check_cancel.

  3) The worker thread changes state to THREAD_DONE once the task is
     done, and notifies elem->check_cancel to allow thread_pool_cancel
     to continue execution, and signals the notifier (pool->notifier) to
     allow callback function to be called later. But because of the
     global mutex, the notifier won't get processed until step 4) and 5)
     are done.

  4) thread_pool_cancel continues, leaving the notifier signaled, it
     just returns to caller.

  5) Caller thinks the request is already canceled successfully, so it
     releases any related data, such as freeing elem->common.opaque.

  6) In the next main loop iteration, the notifier handler,
     event_notifier_ready, is called. It finds the canceled thread in
     THREAD_DONE state, so calls elem->common.cb, with an (likely)
     dangling opaque pointer. This is a use-after-free.

Fix it by calling event_notifier_ready before leaving
thread_pool_cancel.

Test case update: This change will let cancel complete earlier than
test-thread-pool.c expects, so update the code to check this case: if
it's already done, done_cb sets .aiocb to NULL, skip calling
bdrv_aio_cancel on them.

Reported-by: Ulrich Obergfell <uobergfe@redhat.com>
Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2014-05-28 14:28:46 +02:00
Dr. David Alan Gilbert 4900116e6f Add a 'name' parameter to qemu_thread_create
If enabled, set the thread name at creation (on GNU systems with
  pthread_set_np)
Fix up all the callers with a thread name

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
2014-03-09 21:09:38 +02:00
Alex Bligh 6a1751b7aa aio / timers: Untangle include files
include/qemu/timer.h has no need to include main-loop.h and
doing so causes an issue for the next patch. Unfortunately
various files assume including timers.h will pull in main-loop.h.
Untangle this mess.

Signed-off-by: Alex Bligh <alex@alex.org.uk>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2013-08-22 19:10:27 +02:00
Stefan Hajnoczi f2e5dca46b aio: drop io_flush argument
The .io_flush() handler no longer exists and has no users.  Drop the
io_flush argument to aio_set_fd_handler() and related functions.

The AioFlushEventNotifierHandler and AioFlushHandler typedefs are no
longer used and are dropped too.

Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2013-08-19 15:52:19 +02:00
Stefan Hajnoczi bb52b14be1 thread-pool: drop thread_pool_active()
.io_flush() is no longer called so drop thread_pool_active().  The block
layer is the only thread-pool.c user and it already tracks in-flight
requests, therefore we do not need thread_pool_active().

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2013-08-19 15:52:19 +02:00
Stefan Hajnoczi c4d9d19645 threadpool: drop global thread pool
Now that each AioContext has a ThreadPool and the main loop AioContext
can be fetched with bdrv_get_aio_context(), we can eliminate the concept
of a global thread pool from thread-pool.c.

The submit functions must take a ThreadPool* argument.

block/raw-posix.c and block/raw-win32.c use
aio_get_thread_pool(bdrv_get_aio_context(bs)) to fetch the main loop's
ThreadPool.

tests/test-thread-pool.c must be updated to reflect the new
thread_pool_submit() function prototypes.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
2013-03-15 16:07:51 +01:00
Stefan Hajnoczi f7311ccc63 threadpool: add thread_pool_new() and thread_pool_free()
ThreadPool is tied to an AioContext through its event notifier, which
dictates in which AioContext the work item's callback function will be
invoked.

In order to support multiple AioContexts we need to support multiple
ThreadPool instances.

This patch adds the new/free functions.  The free function deserves
special attention because it quiesces remaining worker threads.  This
requires a new condition variable and a "stopping" flag to let workers
know they should terminate once idle.

We never needed to do this before since the global threadpool was not
explicitly destroyed until process termination.

Also stash the AioContext pointer in ThreadPool so that we can call
aio_set_event_notifier() in thread_pool_free().  We didn't need to hold
onto AioContext previously since there was no free function.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
2013-03-15 16:07:50 +01:00
Stefan Hajnoczi b811203cf2 threadpool: move globals into struct ThreadPool
Move global variables into a struct so multiple thread pools can be
supported in the future.

This patch does not change thread-pool.h interfaces.  There is still a
global thread pool and it is not yet possible to create/destroy
individual thread pools.  Moving the variables into a struct first makes
later patches easier to review.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
2013-03-15 16:07:50 +01:00
Paolo Bonzini 1de7afc984 misc: move include files to include/qemu/
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2012-12-19 08:32:39 +01:00
Paolo Bonzini 737e150e89 block: move include files to include/block/
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2012-12-19 08:31:31 +01:00
Stefan Hajnoczi d7331bed11 aio: rename AIOPool to AIOCBInfo
Now that AIOPool no longer keeps a freelist, it isn't really a "pool"
anymore.  Rename it to AIOCBInfo and make it const since it no longer
needs to be modified.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2012-11-14 18:19:21 +01:00
Paolo Bonzini 19d092cf9b threadpool: do not take lock in event_notifier_ready
The ordering is:

    worker thread                         consumer thread
    -------------------------------------------------------------------
    write ret                             event_notifier_test_and_clear
    wmb()                                 read state
    write state                           rmb()
    event_notifier_set                    read ret

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2012-10-31 10:38:01 +01:00
Paolo Bonzini d354c7eccf aio: add generic thread-pool facility
Add a generic thread-pool.  The code is roughly based on posix-aio-compat.c,
with some changes, especially the following:

- use QemuSemaphore instead of QemuCond;

- separate the state of the thread from the return code of the worker
function.  The return code is totally opaque for the thread pool;

- do not busy wait when doing cancellation.

A more generic threadpool (but still specific to I/O so that in the future
it can use special scheduling classes or PI mutexes) can have many uses:
it allows more flexibility in raw-posix.c and can more easily be extended
to Win32, and it will also be used to do an msync of the persistent bitmap.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2012-10-31 10:37:48 +01:00