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migration/postcopy: Replace QemuSemaphore with QemuEvent

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thread_sync_sem is an one-shot event so it can be converted into
QemuEvent, which is more lightweight.

Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Link: https://lore.kernel.org/r/20250529-event-v5-9-53b285203794@daynix.com
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Akihiko Odaki 2025-05-29 14:45:58 +09:00 • committed by Paolo Bonzini
parent da926a8b9d
commit d401b7aed8
3 changed files with 8 additions and 8 deletions
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4
migration/migration.h
View file

@ -98,9 +98,9 @@ struct MigrationIncomingState {
void (*transport_cleanup)(void *data); void (*transport_cleanup)(void *data);
/* /*
* Used to sync thread creations. Note that we can't create threads in * Used to sync thread creations. Note that we can't create threads in
* parallel with this sem. * parallel with this event.
*/ */
QemuSemaphore thread_sync_sem; QemuEvent thread_sync_event;
/* /*
* Free at the start of the main state load, set as the main thread finishes * Free at the start of the main state load, set as the main thread finishes
* loading state. * loading state.

10
migration/postcopy-ram.c
View file

@ -90,10 +90,10 @@ void postcopy_thread_create(MigrationIncomingState *mis,
QemuThread *thread, const char *name, QemuThread *thread, const char *name,
void *(*fn)(void *), int joinable) void *(*fn)(void *), int joinable)
{ {
qemu_sem_init(&mis->thread_sync_sem, 0); qemu_event_init(&mis->thread_sync_event, false);
qemu_thread_create(thread, name, fn, mis, joinable); qemu_thread_create(thread, name, fn, mis, joinable);
qemu_sem_wait(&mis->thread_sync_sem); qemu_event_wait(&mis->thread_sync_event);
qemu_sem_destroy(&mis->thread_sync_sem); qemu_event_destroy(&mis->thread_sync_event);
} }
/* Postcopy needs to detect accesses to pages that haven't yet been copied /* Postcopy needs to detect accesses to pages that haven't yet been copied
@ -964,7 +964,7 @@ static void *postcopy_ram_fault_thread(void *opaque)
trace_postcopy_ram_fault_thread_entry(); trace_postcopy_ram_fault_thread_entry();
rcu_register_thread(); rcu_register_thread();
mis->last_rb = NULL; /* last RAMBlock we sent part of */ mis->last_rb = NULL; /* last RAMBlock we sent part of */
qemu_sem_post(&mis->thread_sync_sem); qemu_event_set(&mis->thread_sync_event);
struct pollfd *pfd; struct pollfd *pfd;
size_t pfd_len = 2 + mis->postcopy_remote_fds->len; size_t pfd_len = 2 + mis->postcopy_remote_fds->len;
@ -1716,7 +1716,7 @@ void *postcopy_preempt_thread(void *opaque)
rcu_register_thread(); rcu_register_thread();
qemu_sem_post(&mis->thread_sync_sem); qemu_event_set(&mis->thread_sync_event);
/* /*
* The preempt channel is established in asynchronous way. Wait * The preempt channel is established in asynchronous way. Wait

2
migration/savevm.c
View file

@ -2078,7 +2078,7 @@ static void *postcopy_ram_listen_thread(void *opaque)
migrate_set_state(&mis->state, MIGRATION_STATUS_ACTIVE, migrate_set_state(&mis->state, MIGRATION_STATUS_ACTIVE,
MIGRATION_STATUS_POSTCOPY_ACTIVE); MIGRATION_STATUS_POSTCOPY_ACTIVE);
qemu_sem_post(&mis->thread_sync_sem); qemu_event_set(&mis->thread_sync_event);
trace_postcopy_ram_listen_thread_start(); trace_postcopy_ram_listen_thread_start();
rcu_register_thread(); rcu_register_thread();