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* qemu-thread: Use futex if available for QemuLockCntAkihiko Odaki2025-06-061-3/+4
| | | | | | | | This unlocks the futex-based implementation of QemuLockCnt to Windows. Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com> Link: https://lore.kernel.org/r/20250529-event-v5-6-53b285203794@daynix.com Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
* futex: Support WindowsAkihiko Odaki2025-06-061-1/+1
| | | | | | | | | Windows supports futex-like APIs since Windows 8 and Windows Server 2012. Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com> Link: https://lore.kernel.org/r/20250529-event-v5-2-53b285203794@daynix.com Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
* include: Move QemuLockCnt APIs to their own headerPeter Maydell2024-10-151-0/+1
| | | | | | | | | | | | | | | | | | | | | | Currently the QemuLockCnt data structure and associated functions are in the include/qemu/thread.h header. Move them to their own qemu/lockcnt.h. The main reason for doing this is that it means we can autogenerate the documentation comments into the docs/devel documentation. The copyright/author in the new header is drawn from lockcnt.c, since the header changes were added in the same commit as lockcnt.c; since neither thread.h nor lockcnt.c state an explicit license, the standard default of GPL-2-or-later applies. We include the new header (and the .c file, which was accidentally omitted previously) in the "RCU" part of MAINTAINERS, since that is where the lockcnt.rst documentation is categorized. Signed-off-by: Peter Maydell <peter.maydell@linaro.org> Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org> Acked-by: Paolo Bonzini <pbonzini@redhat.com> Message-id: 20240816132212.3602106-7-peter.maydell@linaro.org
* qemu/atomic.h: rename atomic_ to qatomic_Stefan Hajnoczi2020-09-231-25/+27
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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>
* qemu-thread: optimize QemuLockCnt with futexes on LinuxPaolo Bonzini2017-01-161-0/+283
| | | | | | | | | | 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>
* qemu-thread: introduce QemuLockCntPaolo Bonzini2017-01-161-0/+114
A QemuLockCnt comprises a counter and a mutex, with primitives to increment and decrement the counter, and to take and release the mutex. It can be used to do lock-free visits to a data structure whenever mutexes would be too heavy-weight and the critical section is too long for RCU. This could be implemented simply by protecting the counter with the mutex, but QemuLockCnt is harder to misuse and more efficient. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Reviewed-by: Fam Zheng <famz@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Message-id: 20170112180800.21085-3-pbonzini@redhat.com Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>