On 2023/12/13 0:39, Stefan Hajnoczi wrote:
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@xxxxxxxxxx>
Reviewed-by: Paul Durrant <paul@xxxxxxx>
Acked-by: Fabiano Rosas <farosas@xxxxxxx>
Acked-by: David Woodhouse <dwmw@xxxxxxxxxxxx>
Reviewed-by: Cédric Le Goater <clg@xxxxxxxx>
Acked-by: Peter Xu <peterx@xxxxxxxxxx>
Acked-by: Eric Farman <farman@xxxxxxxxxxxxx>
Reviewed-by: Harsh Prateek Bora <harshpb@xxxxxxxxxxxxx>
---
include/block/aio-wait.h | 2 +-
include/qemu/main-loop.h | 40 ++++-----
include/qemu/thread.h | 2 +-
accel/accel-blocker.c | 10 +--
accel/dummy-cpus.c | 8 +-
accel/hvf/hvf-accel-ops.c | 4 +-
accel/kvm/kvm-accel-ops.c | 4 +-
accel/kvm/kvm-all.c | 22 ++---
accel/tcg/cpu-exec.c | 26 +++---
accel/tcg/cputlb.c | 16 ++--
accel/tcg/tcg-accel-ops-icount.c | 4 +-
accel/tcg/tcg-accel-ops-mttcg.c | 12 +--
accel/tcg/tcg-accel-ops-rr.c | 14 ++--
accel/tcg/tcg-accel-ops.c | 2 +-
accel/tcg/translate-all.c | 2 +-
cpu-common.c | 4 +-
dump/dump.c | 4 +-
hw/core/cpu-common.c | 6 +-
hw/i386/intel_iommu.c | 6 +-
hw/i386/kvm/xen_evtchn.c | 16 ++--
hw/i386/kvm/xen_overlay.c | 2 +-
hw/i386/kvm/xen_xenstore.c | 2 +-
hw/intc/arm_gicv3_cpuif.c | 2 +-
hw/intc/s390_flic.c | 18 ++--
hw/misc/edu.c | 4 +-
hw/misc/imx6_src.c | 2 +-
hw/misc/imx7_src.c | 2 +-
hw/net/xen_nic.c | 8 +-
hw/ppc/pegasos2.c | 2 +-
hw/ppc/ppc.c | 4 +-
hw/ppc/spapr.c | 2 +-
hw/ppc/spapr_rng.c | 4 +-
hw/ppc/spapr_softmmu.c | 4 +-
hw/remote/mpqemu-link.c | 20 ++---
hw/remote/vfio-user-obj.c | 2 +-
hw/s390x/s390-skeys.c | 2 +-
migration/block-dirty-bitmap.c | 4 +-
migration/block.c | 16 ++--
migration/colo.c | 60 +++++++-------
migration/dirtyrate.c | 12 +--
migration/migration.c | 52 ++++++------
migration/ram.c | 12 +--
replay/replay-internal.c | 2 +-
semihosting/console.c | 8 +-
stubs/iothread-lock.c | 6 +-
system/cpu-throttle.c | 4 +-
system/cpus.c | 51 ++++++------
system/dirtylimit.c | 4 +-
system/memory.c | 2 +-
system/physmem.c | 8 +-
system/runstate.c | 2 +-
system/watchpoint.c | 4 +-
target/arm/arm-powerctl.c | 14 ++--
target/arm/helper.c | 4 +-
target/arm/hvf/hvf.c | 8 +-
target/arm/kvm.c | 4 +-
target/arm/kvm64.c | 4 +-
target/arm/ptw.c | 6 +-
target/arm/tcg/helper-a64.c | 8 +-
target/arm/tcg/m_helper.c | 6 +-
target/arm/tcg/op_helper.c | 24 +++---
target/arm/tcg/psci.c | 2 +-
target/hppa/int_helper.c | 8 +-
target/i386/hvf/hvf.c | 6 +-
target/i386/kvm/hyperv.c | 4 +-
target/i386/kvm/kvm.c | 28 +++----
target/i386/kvm/xen-emu.c | 14 ++--
target/i386/nvmm/nvmm-accel-ops.c | 4 +-
target/i386/nvmm/nvmm-all.c | 20 ++---
target/i386/tcg/sysemu/fpu_helper.c | 6 +-
target/i386/tcg/sysemu/misc_helper.c | 4 +-
target/i386/whpx/whpx-accel-ops.c | 4 +-
target/i386/whpx/whpx-all.c | 24 +++---
target/loongarch/csr_helper.c | 4 +-
target/mips/kvm.c | 4 +-
target/mips/tcg/sysemu/cp0_helper.c | 4 +-
target/openrisc/sys_helper.c | 16 ++--
target/ppc/excp_helper.c | 12 +--
target/ppc/kvm.c | 4 +-
target/ppc/misc_helper.c | 8 +-
target/ppc/timebase_helper.c | 8 +-
target/s390x/kvm/kvm.c | 4 +-
target/s390x/tcg/misc_helper.c | 118 +++++++++++++--------------
target/sparc/int32_helper.c | 2 +-
target/sparc/int64_helper.c | 6 +-
target/sparc/win_helper.c | 20 ++---
target/xtensa/exc_helper.c | 8 +-
ui/spice-core.c | 4 +-
util/async.c | 2 +-
util/main-loop.c | 8 +-
util/qsp.c | 6 +-
util/rcu.c | 14 ++--
audio/coreaudio.m | 4 +-
memory_ldst.c.inc | 18 ++--
target/i386/hvf/README.md | 2 +-
ui/cocoa.m | 50 ++++++------
96 files changed, 530 insertions(+), 529 deletions(-)
diff --git a/include/block/aio-wait.h b/include/block/aio-wait.h
index 5449b6d742..d22ca24329 100644
--- a/include/block/aio-wait.h
+++ b/include/block/aio-wait.h
@@ -151,7 +151,7 @@ static inline bool in_aio_context_home_thread(AioContext *ctx)
}
if (ctx == qemu_get_aio_context()) {
- return qemu_mutex_iothread_locked();
+ return bql_locked();
} else {
return false;
}
diff --git a/include/qemu/main-loop.h b/include/qemu/main-loop.h
index 68e70e61aa..596a206acd 100644
--- a/include/qemu/main-loop.h
+++ b/include/qemu/main-loop.h
@@ -248,19 +248,19 @@ GSource *iohandler_get_g_source(void);
AioContext *iohandler_get_aio_context(void);
/**
- * qemu_mutex_iothread_locked: Return lock status of the main loop mutex.
+ * bql_locked: Return lock status of the Big QEMU Lock (BQL)
*
- * The main loop mutex is the coarsest lock in QEMU, and as such it
+ * The Big QEMU Lock (BQL) is the coarsest lock in QEMU, and as such it
* 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.
+ * thread is running within the BQL.
*
* 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);
+bool bql_locked(void);
/**
* qemu_in_main_thread: return whether it's possible to safely access
@@ -312,58 +312,58 @@ bool qemu_in_main_thread(void);
} while (0)
/**
- * qemu_mutex_lock_iothread: Lock the main loop mutex.
+ * bql_lock: Lock the Big QEMU Lock (BQL).
*
- * This function locks the main loop mutex. The mutex is taken by
+ * This function locks the Big QEMU Lock (BQL). The lock is taken by
* main() in vl.c and always taken except while waiting on
- * external events (such as with select). The mutex should be taken
+ * external events (such as with select). The lock should be taken
* by threads other than the main loop thread when calling
* qemu_bh_new(), qemu_set_fd_handler() and basically all other
* functions documented in this file.
*
- * NOTE: tools currently are single-threaded and qemu_mutex_lock_iothread
+ * NOTE: tools currently are single-threaded and bql_lock
* is a no-op there.
*/
-#define qemu_mutex_lock_iothread() \
- qemu_mutex_lock_iothread_impl(__FILE__, __LINE__)
-void qemu_mutex_lock_iothread_impl(const char *file, int line);
+#define bql_lock() \
+ bql_lock_impl(__FILE__, __LINE__)
This line break is no longer necessary.
