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2014-07-09AioContext: speed up aio_notifyPaolo Bonzini1-1/+18
In many cases, the call to event_notifier_set in aio_notify is unnecessary. In particular, if we are executing aio_dispatch, or if aio_poll is not blocking, we know that we will soon get to the next loop iteration (if necessary); the thread that hosts the AioContext's event loop does not need any nudging. The patch includes a Promela formal model that shows that this really works and does not need any further complication such as generation counts. It needs a memory barrier though. The generation counts are not needed because any change to ctx->dispatching after the memory barrier is okay for aio_notify. If it changes from zero to one, it is the right thing to skip event_notifier_set. If it changes from one to zero, the event_notifier_set is unnecessary but harmless. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2014-06-04aio: fix qemu_bh_schedule() bh->ctx race conditionStefan Hajnoczi1-4/+10
qemu_bh_schedule() is supposed to be thread-safe at least the first time it is called. Unfortunately this is not quite true: bh->scheduled = 1; aio_notify(bh->ctx); Since another thread may run the BH callback once it has been scheduled, there is a race condition if the callback frees the BH before aio_notify(bh->ctx) has a chance to run. Reported-by: Stefan Priebe <s.priebe@profihost.ag> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> Reviewed-by: Paolo Bonzini <pbonzini@redhat.com> Tested-by: Stefan Priebe <s.priebe@profihost.ag>
2014-03-13aio: add aio_context_acquire() and aio_context_release()Stefan Hajnoczi1-0/+18
It can be useful to run an AioContext from a thread which normally does not "own" the AioContext. For example, request draining can be implemented by acquiring the AioContext and looping aio_poll() until all requests have been completed. The following pattern should work: /* Event loop thread */ while (running) { aio_context_acquire(ctx); aio_poll(ctx, true); aio_context_release(ctx); } /* Another thread */ aio_context_acquire(ctx); bdrv_read(bs, 0x1000, buf, 1); aio_context_release(ctx); This patch implements aio_context_acquire() and aio_context_release(). Note that existing aio_poll() callers do not need to worry about acquiring and releasing - it is only needed when multiple threads will call aio_poll() on the same AioContext. Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2013-08-22aio / timers: aio_ctx_prepare sets timeout from AioContext timersAlex Bligh1-1/+12
Calculate the timeout in aio_ctx_prepare taking into account the timers attached to the AioContext. Alter aio_ctx_check similarly. Signed-off-by: Alex Bligh <alex@alex.org.uk> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2013-08-22aio / timers: Add a notify callback to QEMUTimerListAlex Bligh1-1/+6
Add a notify pointer to QEMUTimerList so it knows what to notify on a timer change. Signed-off-by: Alex Bligh <alex@alex.org.uk> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2013-08-22aio / timers: Add QEMUTimerListGroup to AioContextAlex Bligh1-0/+2
Add a QEMUTimerListGroup each AioContext (meaning a QEMUTimerList associated with each clock is added) and delete it when the AioContext is freed. Signed-off-by: Alex Bligh <alex@alex.org.uk> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2013-08-19aio: drop io_flush argumentStefan Hajnoczi1-2/+2
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>
2013-07-19QEMUBH: make AioContext's bh re-entrantLiu Ping Fan1-2/+31
BH will be used outside big lock, so introduce lock to protect between the writers, ie, bh's adders and deleter. The lock only affects the writers and bh's callback does not take this extra lock. Note that for the same AioContext, aio_bh_poll() can not run in parallel yet. Signed-off-by: Liu Ping Fan <pingfank@linux.vnet.ibm.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2013-03-15aio: add a ThreadPool instance to AioContextStefan Hajnoczi1-0/+11
This patch adds a ThreadPool to AioContext. It's possible that some AioContext instances will never use the ThreadPool, so defer creation until aio_get_thread_pool(). The reason why AioContext should have the ThreadPool is because the ThreadPool is bound to a AioContext instance where the work item's callback function is invoked. It doesn't make sense to keep the ThreadPool pointer anywhere other than AioContext. For example, block/raw-posix.c can get its AioContext's ThreadPool and submit work. Special note about headers: I used struct ThreadPool in aio.h because there is a circular dependency if aio.h includes thread-pool.h. Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
2013-02-21aio: convert aio_poll() to g_poll(3)Stefan Hajnoczi1-0/+2
AioHandler already has a GPollFD so we can directly use its events/revents. Add the int pollfds_idx field to AioContext so we can map g_poll(3) results back to AioHandlers. Reuse aio_dispatch() to invoke handlers after g_poll(3). Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> Reviewed-by: Laszlo Ersek <lersek@redhat.com> Message-id: 1361356113-11049-10-git-send-email-stefanha@redhat.com Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
2012-12-19misc: move include files to include/qemu/Paolo Bonzini1-1/+1
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2012-12-19block: move include files to include/block/Paolo Bonzini1-1/+1
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2012-12-11aio: Get rid of qemu_aio_flush()Kevin Wolf1-5/+0
There are no remaining users, and new users should probably be using bdrv_drain_all() in the first place. Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2012-11-12aio: fix aio_ctx_prepare with idle bottom halvesPaolo Bonzini1-4/+2
Commit ed2aec4867f0d5f5de496bb765347b5d0cfe113d changed the return value of aio_ctx_prepare from false to true when only idle bottom halves are available. This broke PC old-style DMA, which uses them. Fix this by making aio_ctx_prepare return true only when non-idle bottom halves are scheduled to run. Reported-by: malc <av1474@comtv.ru> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: malc <av1474@comtv.ru>
2012-10-30aio: clean up now-unused functionsPaolo Bonzini1-16/+7
Some cleanups can now be made, now that the main loop does not anymore need hooks into the bottom half code. Reviewed-by: Anthony Liguori <aliguori@us.ibm.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2012-10-30aio: add aio_notifyPaolo Bonzini1-4/+26
With this change async.c does not rely anymore on any service from main-loop.c, i.e. it is completely self-contained. Reviewed-by: Anthony Liguori <aliguori@us.ibm.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2012-10-30aio: make AioContexts GSourcesPaolo Bonzini1-1/+64
This lets AioContexts be used (optionally) with a glib main loop. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2012-10-30aio: add non-blocking variant of aio_waitPaolo Bonzini1-1/+1
This will be used when polling the GSource attached to an AioContext. Reviewed-by: Anthony Liguori <aliguori@us.ibm.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2012-10-30aio: add I/O handlers to the AioContext interfacePaolo Bonzini1-0/+6
With this patch, I/O handlers (including event notifier handlers) can be attached to a single AioContext. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2012-10-30aio: introduce AioContext, move bottom halves therePaolo Bonzini1-15/+15
Start introducing AioContext, which will let us remove globals from aio.c/async.c, and introduce multiple I/O threads. The bottom half functions now take an additional AioContext argument. A bottom half is created with a specific AioContext that remains the same throughout the lifetime. qemu_bh_new is just a wrapper that uses a global context. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2012-05-01async: Use bool for boolean struct members and remove a holeStefan Weil1-3/+3
Using bool reduces the size of the structure and improves readability. A hole in the structure was removed. Signed-off-by: Stefan Weil <sw@weilnetz.de> Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
2012-04-26main_loop_wait: block indefinitelyStefano Stabellini1-1/+1
- remove qemu_calculate_timeout; - explicitly size timeout to uint32_t; - introduce slirp_update_timeout; - pass NULL as timeout argument to select in case timeout is the maximum value; Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com> Acked-by: Paul Brook <paul@codesourcery.com> Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
2011-10-21main-loop: create main-loop.hPaolo Bonzini1-0/+1
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2011-09-06async: Allow nested qemu_bh_poll callsKevin Wolf1-8/+16
qemu may segfault when a BH handler first deletes a BH and then (possibly indirectly) calls a nested qemu_bh_poll(). This is because the inner instance frees the BH and deletes it from the list that the outer one processes. This patch deletes BHs only in the outermost qemu_bh_poll instance. Commit 7887f620 already tried to achieve the same, but it assumed that the BH handler would only delete its own BH. With a nested qemu_bh_poll(), this isn't guaranteed, so that commit wasn't enough. Hope this one fixes it for real. Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2011-08-20Use glib memory allocation and free functionsAnthony Liguori1-2/+2
qemu_malloc/qemu_free no longer exist after this commit. Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
2011-08-02async: Remove AsyncContextKevin Wolf1-91/+7
The purpose of AsyncContexts was to protect qcow and qcow2 against reentrancy during an emulated bdrv_read/write (which includes a qemu_aio_wait() call and can run AIO callbacks of different requests if it weren't for AsyncContexts). Now both qcow and qcow2 are protected by CoMutexes and AsyncContexts can be removed. Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2011-06-15Allow nested qemu_bh_poll() after BH deletionKevin Wolf1-2/+3
Without this, qemu segfaults when a BH handler first deletes its BH and then calls another function which involves a nested qemu_bh_poll() call. This can be reproduced by generating an I/O error (e.g. with blkdebug) on an IDE device and using rerror/werror=stop to stop the VM. When continuing the VM, qemu segfaults. Signed-off-by: Kevin Wolf <kwolf@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
2009-10-27Introduce contexts for asynchronous callbacksKevin Wolf1-7/+93
Add the possibility to use AIO and BHs without allowing foreign callbacks to be run. Basically, you put your own AIOs and BHs in a separate context. For details see the comments in the source. Signed-off-by: Kevin Wolf <kwolf@redhat.com> Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
2009-10-27Split out bottom halvesKevin Wolf1-0/+130
Instead of putting more and more stuff into vl.c, let's have the generic functions that deal with asynchronous callbacks in their own file. Signed-off-by: Kevin Wolf <kwolf@redhat.com> Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
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