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system/cpus: rename qemu_mutex_lock_iothread() to bql_lock()

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The Big QEMU Lock (BQL) has many names and they are confusing. The
actual QemuMutex variable is called qemu_global_mutex but it's commonly
referred to as the BQL in discussions and some code comments. The
locking APIs, however, are called qemu_mutex_lock_iothread() and
qemu_mutex_unlock_iothread().

The "iothread" name is historic and comes from when the main thread was
split into into KVM vcpu threads and the "iothread" (now called the main
loop thread). I have contributed to the confusion myself by introducing
a separate --object iothread, a separate concept unrelated to the BQL.

The "iothread" name is no longer appropriate for the BQL. Rename the
locking APIs to:
- void bql_lock(void)
- void bql_unlock(void)
- bool bql_locked(void)

There are more APIs with "iothread" in their names. Subsequent patches
will rename them. There are also comments and documentation that will be
updated in later patches.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Paul Durrant <paul@xen.org>
Acked-by: Fabiano Rosas <farosas@suse.de>
Acked-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Cédric Le Goater <clg@kaod.org>
Acked-by: Peter Xu <peterx@redhat.com>
Acked-by: Eric Farman <farman@linux.ibm.com>
Reviewed-by: Harsh Prateek Bora <harshpb@linux.ibm.com>
Acked-by: Hyman Huang <yong.huang@smartx.com>
Reviewed-by: Akihiko Odaki <akihiko.odaki@daynix.com>
Message-id: 20240102153529.486531-2-stefanha@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Stefan Hajnoczi 2024-01-02 10:35:25 -05:00
parent 897a06c6d7
commit 195801d700
95 changed files with 529 additions and 529 deletions
Download patch file Download diff file Expand all files Collapse all files

20
hw/remote/mpqemu-link.c
View file

@ -33,7 +33,7 @@
*/
bool mpqemu_msg_send(MPQemuMsg *msg, QIOChannel *ioc, Error **errp)
{
bool iolock = qemu_mutex_iothread_locked();
bool drop_bql = bql_locked();
bool iothread = qemu_in_iothread();
struct iovec send[2] = {};
int *fds = NULL;
@ -63,8 +63,8 @@ bool mpqemu_msg_send(MPQemuMsg *msg, QIOChannel *ioc, Error **errp)
* for IOThread case.
* Also skip lock handling while in a co-routine in the main context.
*/
if (iolock && !iothread && !qemu_in_coroutine()) {
qemu_mutex_unlock_iothread();
if (drop_bql && !iothread && !qemu_in_coroutine()) {
bql_unlock();
}
if (!qio_channel_writev_full_all(ioc, send, G_N_ELEMENTS(send),
@ -74,9 +74,9 @@ bool mpqemu_msg_send(MPQemuMsg *msg, QIOChannel *ioc, Error **errp)
trace_mpqemu_send_io_error(msg->cmd, msg->size, nfds);
}
if (iolock && !iothread && !qemu_in_coroutine()) {
if (drop_bql && !iothread && !qemu_in_coroutine()) {
/* See above comment why skip locking here. */
qemu_mutex_lock_iothread();
bql_lock();
}
return ret;
@ -96,7 +96,7 @@ static ssize_t mpqemu_read(QIOChannel *ioc, void *buf, size_t len, int **fds,
size_t *nfds, Error **errp)
{
struct iovec iov = { .iov_base = buf, .iov_len = len };
bool iolock = qemu_mutex_iothread_locked();
bool drop_bql = bql_locked();
bool iothread = qemu_in_iothread();
int ret = -1;
@ -106,14 +106,14 @@ static ssize_t mpqemu_read(QIOChannel *ioc, void *buf, size_t len, int **fds,
*/
assert(qemu_in_coroutine() || !iothread);
if (iolock && !iothread && !qemu_in_coroutine()) {
qemu_mutex_unlock_iothread();
if (drop_bql && !iothread && !qemu_in_coroutine()) {
bql_unlock();
}
ret = qio_channel_readv_full_all_eof(ioc, &iov, 1, fds, nfds, errp);
if (iolock && !iothread && !qemu_in_coroutine()) {
qemu_mutex_lock_iothread();
if (drop_bql && !iothread && !qemu_in_coroutine()) {
bql_lock();
}
return (ret <= 0) ? ret : iov.iov_len;

2
hw/remote/vfio-user-obj.c
View file

@ -400,7 +400,7 @@ static int vfu_object_mr_rw(MemoryRegion *mr, uint8_t *buf, hwaddr offset,
}
if (release_lock) {
qemu_mutex_unlock_iothread();
bql_unlock();
release_lock = false;
}