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migration: Add postcopy_thread_create() 

Postcopy create threads. A common manner is we init a sem and use it to sync
with the thread.  Namely, we have fault_thread_sem and listen_thread_sem and
they're only used for this.

Make it a shared infrastructure so it's easier to create yet another thread.

Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
Message-Id: <20220301083925.33483-7-peterx@redhat.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
This commit is contained in:
Peter Xu 2022-03-01 16:39:06 +08:00 committed by Dr. David Alan Gilbert
parent cfc7dc8abf
commit 095c12a4a2
4 changed files with 29 additions and 18 deletions
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8
migration/migration.h
View File

@ -70,7 +70,11 @@ struct MigrationIncomingState {
/* A hook to allow cleanup at the end of incoming migration */
void *transport_data;
void (*transport_cleanup)(void *data);
/*
* Used to sync thread creations. Note that we can't create threads in
* parallel with this sem.
*/
QemuSemaphore thread_sync_sem;
/*
* Free at the start of the main state load, set as the main thread finishes
* loading state.
@ -83,13 +87,11 @@ struct MigrationIncomingState {
size_t largest_page_size;
bool have_fault_thread;
QemuThread fault_thread;
QemuSemaphore fault_thread_sem;
/* Set this when we want the fault thread to quit */
bool fault_thread_quit;
bool have_listen_thread;
QemuThread listen_thread;
QemuSemaphore listen_thread_sem;
/* For the kernel to send us notifications */
int userfault_fd;

23
migration/postcopy-ram.c
View File

@ -78,6 +78,20 @@ int postcopy_notify(enum PostcopyNotifyReason reason, Error **errp)
&pnd);
}
/*
* NOTE: this routine is not thread safe, we can't call it concurrently. But it
* should be good enough for migration's purposes.
*/
void postcopy_thread_create(MigrationIncomingState *mis,
QemuThread *thread, const char *name,
void *(*fn)(void *), int joinable)
{
qemu_sem_init(&mis->thread_sync_sem, 0);
qemu_thread_create(thread, name, fn, mis, joinable);
qemu_sem_wait(&mis->thread_sync_sem);
qemu_sem_destroy(&mis->thread_sync_sem);
}
/* Postcopy needs to detect accesses to pages that haven't yet been copied
* across, and efficiently map new pages in, the techniques for doing this
* are target OS specific.
@ -902,7 +916,7 @@ static void *postcopy_ram_fault_thread(void *opaque)
trace_postcopy_ram_fault_thread_entry();
rcu_register_thread();
mis->last_rb = NULL; /* last RAMBlock we sent part of */
qemu_sem_post(&mis->fault_thread_sem);
qemu_sem_post(&mis->thread_sync_sem);
struct pollfd *pfd;
size_t pfd_len = 2 + mis->postcopy_remote_fds->len;
@ -1173,11 +1187,8 @@ int postcopy_ram_incoming_setup(MigrationIncomingState *mis)
return -1;
}
qemu_sem_init(&mis->fault_thread_sem, 0);
qemu_thread_create(&mis->fault_thread, "postcopy/fault",
postcopy_ram_fault_thread, mis, QEMU_THREAD_JOINABLE);
qemu_sem_wait(&mis->fault_thread_sem);
qemu_sem_destroy(&mis->fault_thread_sem);
postcopy_thread_create(mis, &mis->fault_thread, "postcopy/fault",
postcopy_ram_fault_thread, QEMU_THREAD_JOINABLE);
mis->have_fault_thread = true;
/* Mark so that we get notified of accesses to unwritten areas */

4
migration/postcopy-ram.h
View File

@ -135,6 +135,10 @@ void postcopy_remove_notifier(NotifierWithReturn *n);
/* Call the notifier list set by postcopy_add_start_notifier */
int postcopy_notify(enum PostcopyNotifyReason reason, Error **errp);
void postcopy_thread_create(MigrationIncomingState *mis,
QemuThread *thread, const char *name,
void *(*fn)(void *), int joinable);
struct PostCopyFD;
/* ufd is a pointer to the struct uffd_msg *TODO: more Portable! */

12
migration/savevm.c
View File

@ -1863,7 +1863,7 @@ static void *postcopy_ram_listen_thread(void *opaque)
migrate_set_state(&mis->state, MIGRATION_STATUS_ACTIVE,
MIGRATION_STATUS_POSTCOPY_ACTIVE);
qemu_sem_post(&mis->listen_thread_sem);
qemu_sem_post(&mis->thread_sync_sem);
trace_postcopy_ram_listen_thread_start();
rcu_register_thread();
@ -1988,14 +1988,8 @@ static int loadvm_postcopy_handle_listen(MigrationIncomingState *mis)
}
mis->have_listen_thread = true;
/* Start up the listening thread and wait for it to signal ready */
qemu_sem_init(&mis->listen_thread_sem, 0);
qemu_thread_create(&mis->listen_thread, "postcopy/listen",
postcopy_ram_listen_thread, NULL,
QEMU_THREAD_DETACHED);
qemu_sem_wait(&mis->listen_thread_sem);
qemu_sem_destroy(&mis->listen_thread_sem);
postcopy_thread_create(mis, &mis->listen_thread, "postcopy/listen",
postcopy_ram_listen_thread, QEMU_THREAD_DETACHED);
trace_loadvm_postcopy_handle_listen("return");
return 0;