QemuEvent is currently broken on ARM due to missing memory barriers
after qatomic_*(). Apart from adding the memory barrier, a closer look
reveals some unpaired memory barriers that are not really needed and
complicated the functions unnecessarily. Also, it is relying on
a memory barrier in ResetEvent(); the barrier _ought_ to be there
but there is really no documentation about it, so make it explicit.
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Usually, we let upper layers handle CPU pinning, because
pthread_setaffinity_np() (-> sched_setaffinity()) is blocked via
seccomp when starting QEMU with
-sandbox enable=on,resourcecontrol=deny
However, we want to configure and observe the CPU affinity of threads
from QEMU directly in some cases when the sandbox option is either not
enabled or not active yet.
So let's add a way to configure CPU pinning via
qemu_thread_set_affinity() and obtain CPU affinity via
qemu_thread_get_affinity() and implement them under POSIX using
pthread_setaffinity_np() + pthread_getaffinity_np().
Implementation under Windows is possible using SetProcessAffinityMask()
+ GetProcessAffinityMask(), however, that is left as future work.
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>
Message-Id: <20221014134720.168738-3-david@redhat.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
As described in:
https://learn.microsoft.com/en-us/visualstudio/debugger/how-to-set-a-thread-name-in-native-code?view=vs-2022
SetThreadDescription() is available since Windows 10, version 1607 and
in some versions only by "Run Time Dynamic Linking". Its declaration is
not yet in mingw, so we lookup the function the same way glib does.
Tested with Visual Studio Community 2022 debugger.
Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Acked-by: Richard Henderson <richard.henderson@linaro.org>
Create macros for file+line expansion in qemu_rec_mutex_unlock
like we have for qemu_mutex_unlock.
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20210614233143.1221879-5-richard.henderson@linaro.org>
clang's C11 atomic_fetch_*() functions only take a C11 atomic type
pointer argument. QEMU uses direct types (int, etc) and this causes a
compiler error when a QEMU code calls these functions in a source file
that also included <stdatomic.h> via a system header file:
$ CC=clang CXX=clang++ ./configure ... && make
../util/async.c:79:17: error: address argument to atomic operation must be a pointer to _Atomic type ('unsigned int *' invalid)
Avoid using atomic_*() names in QEMU's atomic.h since that namespace is
used by <stdatomic.h>. Prefix QEMU's APIs with 'q' so that atomic.h
and <stdatomic.h> can co-exist. I checked /usr/include on my machine and
searched GitHub for existing "qatomic_" users but there seem to be none.
This patch was generated using:
$ git grep -h -o '\<atomic\(64\)\?_[a-z0-9_]\+' include/qemu/atomic.h | \
sort -u >/tmp/changed_identifiers
$ for identifier in $(</tmp/changed_identifiers); do
sed -i "s%\<$identifier\>%q$identifier%g" \
$(git grep -I -l "\<$identifier\>")
done
I manually fixed line-wrap issues and misaligned rST tables.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20200923105646.47864-1-stefanha@redhat.com>
I found that there are many spelling errors in the comments of qemu,
so I used the spellcheck tool to check the spelling errors
and finally found some spelling errors in the util folder.
Signed-off-by: zhaolichang <zhaolichang@huawei.com>
Reviewed-by: Alex Bennee <alex.bennee@linaro.org>
Message-Id: <20200917075029.313-6-zhaolichang@huawei.com>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>
The new function is needed to implement conditional sleep for CPU
throttling. It's possible to reuse qemu_sem_timedwait, but it's more
difficult than just add qemu_cond_timedwait.
Also moved compute_abs_deadline function up the code to reuse it in
qemu_cond_timedwait_impl win32.
Signed-off-by: Yury Kotov <yury-kotov@yandex-team.ru>
Message-Id: <20190909131335.16848-2-yury-kotov@yandex-team.ru>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Both qemu & qga build with Vista API by default already, by defining
_WIN32_WINNT 0x0600. Set it globally in osdep.h instead.
This replaces WINVER by _WIN32_WINNT in osdep.h. WINVER doesn't seem
to be really useful these days.
(see also https://blogs.msdn.microsoft.com/oldnewthing/20070411-00/?p=27283)
Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <20181122110039.15972-4-marcandre.lureau@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
The goal of this module is to profile synchronization primitives (i.e.
mutexes, recursive mutexes and condition variables) so that scalability
issues can be quickly diagnosed.
Sync primitives are profiled by QSP based on the vaddr of the object accessed
as well as the call site (file:line_nr). That means the same object called
from two different call sites will be tracked in separate entries, which
might be reported together or separately (see subsequent commit on
call site coalescing).
Some perf numbers:
Host: Intel(R) Core(TM) i7-6700K CPU @ 4.00GHz
Command: taskset -c 0 tests/atomic_add-bench -d 5 -m
- Before: 54.80 Mops/s
- After: 54.75 Mops/s
That is, a negligible slowdown due to the now indirect call to
qemu_mutex_lock. Note that using a branch instead of an indirect
call introduces a more severe slowdown (53.65 Mops/s, i.e. 2% slowdown).
Enabling the profiler (with -p, added in this series) is more interesting:
- No profiling: 54.75 Mops/s
- W/ profiling: 12.53 Mops/s
That is, a 4.36X slowdown.
We can break down this slowdown by removing the get_clock calls or
the entry lookup:
- No profiling: 54.75 Mops/s
- W/o get_clock: 25.37 Mops/s
- W/o entry lookup: 19.30 Mops/s
- W/ profiling: 12.53 Mops/s
Signed-off-by: Emilio G. Cota <cota@braap.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Introduce some hooks for the shared part of qemu thread between POSIX
and Windows implementations. Note that in qemu_mutex_unlock_impl() we
moved the call before unlock operation which should make more sense.
And we don't need qemu_mutex_post_unlock() hook.
Put all these shared hooks into the header files. It should be internal
to qemu-thread but not for qemu-thread users, hence put into util/
directory.
Reviewed-by: Emilio G. Cota <cota@braap.org>
Signed-off-by: Peter Xu <peterx@redhat.com>
Message-Id: <20180425025459.5258-3-peterx@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Not all platforms check whether a lock is initialized before used. In
particular Linux seems to be more permissive than OSX.
Check initialization state explicitly in our code to catch such bugs
earlier.
Signed-off-by: Fam Zheng <famz@redhat.com>
Message-Id: <20170704122325.25634-1-famz@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
These trace events were very useful to help me to understand and find a
reordering issue in vfio, for example:
qemu_mutex_lock locked mutex 0x10905ad8
vfio_region_write (0001:03:00.0:region1+0xc0, 0x2020c, 4)
qemu_mutex_unlock unlocked mutex 0x10905ad8
qemu_mutex_lock locked mutex 0x10905ad8
vfio_region_write (0001:03:00.0:region1+0xc4, 0xa0000, 4)
qemu_mutex_unlock unlocked mutex 0x10905ad8
that also helped me to see the desired result after the fix:
qemu_mutex_lock locked mutex 0x10905ad8
vfio_region_write (0001:03:00.0:region1+0xc0, 0x2000c, 4)
vfio_region_write (0001:03:00.0:region1+0xc4, 0xb0000, 4)
qemu_mutex_unlock unlocked mutex 0x10905ad8
So it could be a good idea to have these traces implemented. It's worth
mentioning that they should be surgically enabled during the debugging,
otherwise it can flood the trace logs with lock/unlock messages.
How to use it:
trace-event qemu_mutex_lock on|off
trace-event qemu_mutex_unlock on|off
or
trace-event qemu_mutex* on|off
Signed-off-by: Jose Ricardo Ziviani <joserz@linux.vnet.ibm.com>
Message-Id: <1493054398-26013-1-git-send-email-joserz@linux.vnet.ibm.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
[Also handle trylock, cond_wait and win32; trace "unlocked" while still
in the critical section, so that "unlocked" always comes before the
next "locked" tracepoint. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
The multithreaded TCG implementation exposed deadlocks in the win32
condition variables: as implemented, qemu_cond_broadcast waited on
receivers, whereas the pthreads API it was intended to emulate does
not. This was causing a deadlock because broadcast was called while
holding the IO lock, as well as all possible waiters blocked on the
same lock.
This patch replaces all the custom synchronisation code for mutexes
and condition variables with native Windows primitives (SRWlocks and
condition variables) with the same semantics as their POSIX
equivalents. To enable that, it requires a Windows Vista or newer host
OS.
Signed-off-by: Andrey Shedel <ashedel@microsoft.com>
[AB: edited commit message]
Signed-off-by: Andrew Baumann <Andrew.Baumann@microsoft.com>
Message-Id: <20170324220141.10104-1-Andrew.Baumann@microsoft.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Use the Intel HAX is kernel-based hardware acceleration module for
Windows (similar to KVM on Linux).
Based on the "target/i386: Add Intel HAX to android emulator" patch
from David Chou <david.j.chou@intel.com>
Signed-off-by: Vincent Palatin <vpalatin@chromium.org>
Message-Id: <7b9cae28a0c379ab459c7a8545c9a39762bd394f.1484045952.git.vpalatin@chromium.org>
[Drop hax_populate_ram stub. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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>
