This is complex, but I think it is reasonably documented in the source.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: 20170112180800.21085-5-pbonzini@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
GRecMutex is new in glib 2.32, so we cannot use it. Introduce
a recursive mutex in qemu-thread instead, which will be used
instead of RFifoLock.
Reviewed-by: Fam Zheng <famz@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <1477565348-5458-20-git-send-email-pbonzini@redhat.com>
Signed-off-by: Fam Zheng <famz@redhat.com>
Do not use the somewhat mysterious atomic_mb_read/atomic_mb_set,
instead make sure that the operations on QemuEvent are annotated
with the desired acquire and release semantics.
In particular, qemu_event_set wakes up the waiting thread, so it must
be a release from the POV of the waker (compare with qemu_mutex_unlock).
And it actually needs a full barrier, because that's the only thing that
provides something like a "load-release".
Use smp_mb_acquire until we have atomic_load_acquire and
atomic_store_release in atomic.h.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Clean up includes so that osdep.h is included first and headers
which it implies are not included manually.
This commit was created with scripts/clean-includes.
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Message-id: 1454089805-5470-6-git-send-email-peter.maydell@linaro.org
QemuEvents are used heavily by call_rcu. We do not want them to be slow,
but the current implementation does a kernel call on every invocation
of qemu_event_* and won't cut it.
So, wrap a Win32 manual-reset event with a fast userspace path. The
states and transitions are the same as for the futex and mutex/condvar
implementations, but the slow path is different of course. The idea
is to reset the Win32 event lazily, as part of a test-reset-test-wait
sequence. Such a sequence is, indeed, how QemuEvents are used by
RCU and other subsystems!
The patch includes a formal model of the algorithm.
Tested-by: Stefan Weil <sw@weilnetz.de>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Stefan Weil <sw@weilnetz.de>
Destructors are the main additional feature of pthread TLS compared
to __thread. If we were using C++ (hint, hint!) we could have used
thread-local objects with a destructor. Since we are not, instead,
we add a simple Notifier-based API.
Note that the notifier must be per-thread as well. We can add a
global list as well later, perhaps.
The Win32 implementation has some complications because a) detached
threads used not to have a QemuThreadData; b) the main thread does
not go through win32_start_routine, so we have to use atexit too.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
Message-id: 1417518350-6167-3-git-send-email-pbonzini@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Warn if no way of setting thread name is available.
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
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>
Add flag storage to qemu-thread-* to store the namethreads flag
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>
This emulates Win32 manual-reset events using futexes or conditional
variables. Typical ways to use them are with multi-producer,
single-consumer data structures, to test for a complex condition whose
elements come from different threads:
for (;;) {
qemu_event_reset(ev);
... test complex condition ...
if (condition is true) {
break;
}
qemu_event_wait(ev);
}
Or more efficiently (but with some duplication):
... evaluate condition ...
while (!condition) {
qemu_event_reset(ev);
... evaluate condition ...
if (!condition) {
qemu_event_wait(ev);
... evaluate condition ...
}
}
QemuEvent provides a very fast userspace path in the common case when
no other thread is waiting, or the event is not changing state.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
