diff options
| -rw-r--r-- | include/qemu/main-loop.h | 24 | ||||
| -rw-r--r-- | softmmu/cpus.c | 5 | ||||
| -rw-r--r-- | stubs/iothread-lock-block.c | 8 | ||||
| -rw-r--r-- | stubs/meson.build | 3 |
4 files changed, 40 insertions, 0 deletions
diff --git a/include/qemu/main-loop.h b/include/qemu/main-loop.h index 8dbc6fcb89..bc42b5939d 100644 --- a/include/qemu/main-loop.h +++ b/include/qemu/main-loop.h @@ -242,10 +242,34 @@ AioContext *iohandler_get_aio_context(void); * must always be taken outside other locks. This function helps * functions take different paths depending on whether the current * thread is running within the main loop mutex. + * + * This function should never be used in the block layer, because + * unit tests, block layer tools and qemu-storage-daemon do not + * have a BQL. + * Please instead refer to qemu_in_main_thread(). */ bool qemu_mutex_iothread_locked(void); /** + * qemu_in_main_thread: return whether it's possible to safely access + * the global state of the block layer. + * + * Global state of the block layer is not accessible from I/O threads + * or worker threads; only from threads that "own" the default + * AioContext that qemu_get_aio_context() returns. For tests, block + * layer tools and qemu-storage-daemon there is a designated thread that + * runs the event loop for qemu_get_aio_context(), and that is the + * main thread. + * + * For emulators, however, any thread that holds the BQL can act + * as the block layer main thread; this will be any of the actual + * main thread, the vCPU threads or the RCU thread. + * + * For clarity, do not use this function outside the block layer. + */ +bool qemu_in_main_thread(void); + +/** * qemu_mutex_lock_iothread: Lock the main loop mutex. * * This function locks the main loop mutex. The mutex is taken by diff --git a/softmmu/cpus.c b/softmmu/cpus.c index d1ff3cfea1..1681844b61 100644 --- a/softmmu/cpus.c +++ b/softmmu/cpus.c @@ -481,6 +481,11 @@ bool qemu_mutex_iothread_locked(void) return get_iothread_locked(); } +bool qemu_in_main_thread(void) +{ + return qemu_mutex_iothread_locked(); +} + /* * The BQL is taken from so many places that it is worth profiling the * callers directly, instead of funneling them all through a single function. diff --git a/stubs/iothread-lock-block.c b/stubs/iothread-lock-block.c new file mode 100644 index 0000000000..c88ed70462 --- /dev/null +++ b/stubs/iothread-lock-block.c @@ -0,0 +1,8 @@ +#include "qemu/osdep.h" +#include "qemu/main-loop.h" + +bool qemu_in_main_thread(void) +{ + return qemu_get_current_aio_context() == qemu_get_aio_context(); +} + diff --git a/stubs/meson.build b/stubs/meson.build index d359cbe1ad..6f80fec761 100644 --- a/stubs/meson.build +++ b/stubs/meson.build @@ -17,6 +17,9 @@ if linux_io_uring.found() stub_ss.add(files('io_uring.c')) endif stub_ss.add(files('iothread-lock.c')) +if have_block + stub_ss.add(files('iothread-lock-block.c')) +endif stub_ss.add(files('isa-bus.c')) stub_ss.add(files('is-daemonized.c')) if libaio.found() |