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

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>

19 files changed, 54 insertions, 54 deletions

diff --git a/hw/core/cpu-common.c b/hw/core/cpu-common.c
index d0e7bbd..3ccfe88 100644
--- a/hw/core/cpu-common.c
+++ b/hw/core/cpu-common.c
@@ -70,14 +70,14 @@ CPUState *cpu_create(const char *typename)
  * BQL here if we need to.  cpu_interrupt assumes it is held.*/
 void cpu_reset_interrupt(CPUState *cpu, int mask)
 {
-    bool need_lock = !qemu_mutex_iothread_locked();
+    bool need_lock = !bql_locked();
 
     if (need_lock) {
-        qemu_mutex_lock_iothread();
+        bql_lock();
     }
     cpu->interrupt_request &= ~mask;
     if (need_lock) {
-        qemu_mutex_unlock_iothread();
+        bql_unlock();
     }
 }
 
diff --git a/hw/i386/intel_iommu.c b/hw/i386/intel_iommu.c
index ed5677c..1a07fad 100644
--- a/hw/i386/intel_iommu.c
+++ b/hw/i386/intel_iommu.c
@@ -1665,7 +1665,7 @@ static bool vtd_switch_address_space(VTDAddressSpace *as)
 {
     bool use_iommu, pt;
     /* Whether we need to take the BQL on our own */
-    bool take_bql = !qemu_mutex_iothread_locked();
+    bool take_bql = !bql_locked();
 
     assert(as);
 
@@ -1683,7 +1683,7 @@ static bool vtd_switch_address_space(VTDAddressSpace *as)
      * it. We'd better make sure we have had it already, or, take it.
      */
     if (take_bql) {
-        qemu_mutex_lock_iothread();
+        bql_lock();
     }
 
     /* Turn off first then on the other */
@@ -1738,7 +1738,7 @@ static bool vtd_switch_address_space(VTDAddressSpace *as)
     }
 
     if (take_bql) {
-        qemu_mutex_unlock_iothread();
+        bql_unlock();
     }
 
     return use_iommu;
diff --git a/hw/i386/kvm/xen_evtchn.c b/hw/i386/kvm/xen_evtchn.c
index 9a5f3ca..4a835a1 100644
--- a/hw/i386/kvm/xen_evtchn.c
+++ b/hw/i386/kvm/xen_evtchn.c
@@ -425,7 +425,7 @@ void xen_evtchn_set_callback_level(int level)
      * effect immediately. That just leaves interdomain loopback as the case
      * which uses the BH.
      */
-    if (!qemu_mutex_iothread_locked()) {
+    if (!bql_locked()) {
         qemu_bh_schedule(s->gsi_bh);
         return;
     }
@@ -459,7 +459,7 @@ int xen_evtchn_set_callback_param(uint64_t param)
      * We need the BQL because set_callback_pci_intx() may call into PCI code,
      * and because we may need to manipulate the old and new GSI levels.
      */
-    assert(qemu_mutex_iothread_locked());
+    assert(bql_locked());
     qemu_mutex_lock(&s->port_lock);
 
     switch (type) {
@@ -1037,7 +1037,7 @@ static int close_port(XenEvtchnState *s, evtchn_port_t port,
     XenEvtchnPort *p = &s->port_table[port];
 
     /* Because it *might* be a PIRQ port */
-    assert(qemu_mutex_iothread_locked());
+    assert(bql_locked());
 
     switch (p->type) {
     case EVTCHNSTAT_closed:
@@ -1104,7 +1104,7 @@ int xen_evtchn_soft_reset(void)
         return -ENOTSUP;
     }
 
-    assert(qemu_mutex_iothread_locked());
+    assert(bql_locked());
 
     qemu_mutex_lock(&s->port_lock);
 
@@ -1601,7 +1601,7 @@ bool xen_evtchn_set_gsi(int gsi, int level)
     XenEvtchnState *s = xen_evtchn_singleton;
     int pirq;
 
-    assert(qemu_mutex_iothread_locked());
+    assert(bql_locked());
 
     if (!s || gsi < 0 || gsi >= IOAPIC_NUM_PINS) {
         return false;
@@ -1712,7 +1712,7 @@ void xen_evtchn_snoop_msi(PCIDevice *dev, bool is_msix, unsigned int vector,
         return;
     }
 
-    assert(qemu_mutex_iothread_locked());
+    assert(bql_locked());
 
     pirq = msi_pirq_target(addr, data);
 
@@ -1749,7 +1749,7 @@ int xen_evtchn_translate_pirq_msi(struct kvm_irq_routing_entry *route,
         return 1; /* Not a PIRQ */
     }
 
-    assert(qemu_mutex_iothread_locked());
+    assert(bql_locked());
 
     pirq = msi_pirq_target(address, data);
     if (!pirq || pirq >= s->nr_pirqs) {
@@ -1796,7 +1796,7 @@ bool xen_evtchn_deliver_pirq_msi(uint64_t address, uint32_t data)
         return false;
     }
 
-    assert(qemu_mutex_iothread_locked());
+    assert(bql_locked());
 
     pirq = msi_pirq_target(address, data);
     if (!pirq || pirq >= s->nr_pirqs) {
diff --git a/hw/i386/kvm/xen_overlay.c b/hw/i386/kvm/xen_overlay.c
index 526f7a6..c68e78a 100644
--- a/hw/i386/kvm/xen_overlay.c
+++ b/hw/i386/kvm/xen_overlay.c
@@ -194,7 +194,7 @@ int xen_overlay_map_shinfo_page(uint64_t gpa)
         return -ENOENT;
     }
 
-    assert(qemu_mutex_iothread_locked());
+    assert(bql_locked());
 
     if (s->shinfo_gpa) {
         /* If removing shinfo page, turn the kernel magic off first */
diff --git a/hw/i386/kvm/xen_xenstore.c b/hw/i386/kvm/xen_xenstore.c
index c3633f7..1a9bc34 100644
--- a/hw/i386/kvm/xen_xenstore.c
+++ b/hw/i386/kvm/xen_xenstore.c
@@ -1341,7 +1341,7 @@ static void fire_watch_cb(void *opaque, const char *path, const char *token)
 {
     XenXenstoreState *s = opaque;
 
-    assert(qemu_mutex_iothread_locked());
+    assert(bql_locked());
 
     /*
      * If there's a response pending, we obviously can't scribble over
diff --git a/hw/intc/arm_gicv3_cpuif.c b/hw/intc/arm_gicv3_cpuif.c
index ab1a005..77c2a6d 100644
--- a/hw/intc/arm_gicv3_cpuif.c
+++ b/hw/intc/arm_gicv3_cpuif.c
@@ -934,7 +934,7 @@ void gicv3_cpuif_update(GICv3CPUState *cs)
     ARMCPU *cpu = ARM_CPU(cs->cpu);
     CPUARMState *env = &cpu->env;
 
-    g_assert(qemu_mutex_iothread_locked());
+    g_assert(bql_locked());
 
     trace_gicv3_cpuif_update(gicv3_redist_affid(cs), cs->hppi.irq,
                              cs->hppi.grp, cs->hppi.prio);
diff --git a/hw/intc/s390_flic.c b/hw/intc/s390_flic.c
index 212f268..f4a8484 100644
--- a/hw/intc/s390_flic.c
+++ b/hw/intc/s390_flic.c
@@ -106,7 +106,7 @@ static int qemu_s390_clear_io_flic(S390FLICState *fs, uint16_t subchannel_id,
     QEMUS390FlicIO *cur, *next;
     uint8_t isc;
 
-    g_assert(qemu_mutex_iothread_locked());
+    g_assert(bql_locked());
     if (!(flic->pending & FLIC_PENDING_IO)) {
         return 0;
     }
@@ -223,7 +223,7 @@ uint32_t qemu_s390_flic_dequeue_service(QEMUS390FLICState *flic)
 {
     uint32_t tmp;
 
-    g_assert(qemu_mutex_iothread_locked());
+    g_assert(bql_locked());
     g_assert(flic->pending & FLIC_PENDING_SERVICE);
     tmp = flic->service_param;
     flic->service_param = 0;
@@ -238,7 +238,7 @@ QEMUS390FlicIO *qemu_s390_flic_dequeue_io(QEMUS390FLICState *flic, uint64_t cr6)
     QEMUS390FlicIO *io;
     uint8_t isc;
 
-    g_assert(qemu_mutex_iothread_locked());
+    g_assert(bql_locked());
     if (!(flic->pending & CR6_TO_PENDING_IO(cr6))) {
         return NULL;
     }
@@ -262,7 +262,7 @@ QEMUS390FlicIO *qemu_s390_flic_dequeue_io(QEMUS390FLICState *flic, uint64_t cr6)
 
 void qemu_s390_flic_dequeue_crw_mchk(QEMUS390FLICState *flic)
 {
-    g_assert(qemu_mutex_iothread_locked());
+    g_assert(bql_locked());
     g_assert(flic->pending & FLIC_PENDING_MCHK_CR);
     flic->pending &= ~FLIC_PENDING_MCHK_CR;
 }
@@ -271,7 +271,7 @@ static void qemu_s390_inject_service(S390FLICState *fs, uint32_t parm)
 {
     QEMUS390FLICState *flic = s390_get_qemu_flic(fs);
 
-    g_assert(qemu_mutex_iothread_locked());
+    g_assert(bql_locked());
     /* multiplexing is good enough for sclp - kvm does it internally as well */
     flic->service_param |= parm;
     flic->pending |= FLIC_PENDING_SERVICE;
@@ -287,7 +287,7 @@ static void qemu_s390_inject_io(S390FLICState *fs, uint16_t subchannel_id,
     QEMUS390FLICState *flic = s390_get_qemu_flic(fs);
     QEMUS390FlicIO *io;
 
-    g_assert(qemu_mutex_iothread_locked());
+    g_assert(bql_locked());
     io = g_new0(QEMUS390FlicIO, 1);
     io->id = subchannel_id;
     io->nr = subchannel_nr;
@@ -304,7 +304,7 @@ static void qemu_s390_inject_crw_mchk(S390FLICState *fs)
 {
     QEMUS390FLICState *flic = s390_get_qemu_flic(fs);
 
-    g_assert(qemu_mutex_iothread_locked());
+    g_assert(bql_locked());
     flic->pending |= FLIC_PENDING_MCHK_CR;
 
     qemu_s390_flic_notify(FLIC_PENDING_MCHK_CR);
@@ -330,7 +330,7 @@ bool qemu_s390_flic_has_crw_mchk(QEMUS390FLICState *flic)
 
 bool qemu_s390_flic_has_any(QEMUS390FLICState *flic)
 {
-    g_assert(qemu_mutex_iothread_locked());
+    g_assert(bql_locked());
     return !!flic->pending;
 }
 
@@ -340,7 +340,7 @@ static void qemu_s390_flic_reset(DeviceState *dev)
     QEMUS390FlicIO *cur, *next;
     int isc;
 
-    g_assert(qemu_mutex_iothread_locked());
+    g_assert(bql_locked());
     flic->simm = 0;
     flic->nimm = 0;
     flic->pending = 0;
diff --git a/hw/misc/edu.c b/hw/misc/edu.c
index e64a246..2a976ca 100644
--- a/hw/misc/edu.c
+++ b/hw/misc/edu.c
@@ -355,9 +355,9 @@ static void *edu_fact_thread(void *opaque)
         smp_mb__after_rmw();
 
         if (qatomic_read(&edu->status) & EDU_STATUS_IRQFACT) {
-            qemu_mutex_lock_iothread();
+            bql_lock();
             edu_raise_irq(edu, FACT_IRQ);
-            qemu_mutex_unlock_iothread();
+            bql_unlock();
         }
     }
 
diff --git a/hw/misc/imx6_src.c b/hw/misc/imx6_src.c
index d20727e..0c60035 100644
--- a/hw/misc/imx6_src.c
+++ b/hw/misc/imx6_src.c
@@ -131,7 +131,7 @@ static void imx6_clear_reset_bit(CPUState *cpu, run_on_cpu_data data)
     struct SRCSCRResetInfo *ri = data.host_ptr;
     IMX6SRCState *s = ri->s;
 
-    assert(qemu_mutex_iothread_locked());
+    assert(bql_locked());
 
     s->regs[SRC_SCR] = deposit32(s->regs[SRC_SCR], ri->reset_bit, 1, 0);
     DPRINTF("reg[%s] <= 0x%" PRIx32 "\n",
diff --git a/hw/misc/imx7_src.c b/hw/misc/imx7_src.c
index 24a0b46..b3725ff 100644
--- a/hw/misc/imx7_src.c
+++ b/hw/misc/imx7_src.c
@@ -136,7 +136,7 @@ static void imx7_clear_reset_bit(CPUState *cpu, run_on_cpu_data data)
     struct SRCSCRResetInfo *ri = data.host_ptr;
     IMX7SRCState *s = ri->s;
 
-    assert(qemu_mutex_iothread_locked());
+    assert(bql_locked());
 
     s->regs[SRC_A7RCR0] = deposit32(s->regs[SRC_A7RCR0], ri->reset_bit, 1, 0);
 
diff --git a/hw/net/xen_nic.c b/hw/net/xen_nic.c
index 1e2b3bae..453fdb9 100644
--- a/hw/net/xen_nic.c
+++ b/hw/net/xen_nic.c
@@ -133,7 +133,7 @@ static bool net_tx_packets(struct XenNetDev *netdev)
     void *page;
     void *tmpbuf = NULL;
 
-    assert(qemu_mutex_iothread_locked());
+    assert(bql_locked());
 
     for (;;) {
         rc = netdev->tx_ring.req_cons;
@@ -260,7 +260,7 @@ static ssize_t net_rx_packet(NetClientState *nc, const uint8_t *buf, size_t size
     RING_IDX rc, rp;
     void *page;
 
-    assert(qemu_mutex_iothread_locked());
+    assert(bql_locked());
 
     if (xen_device_backend_get_state(&netdev->xendev) != XenbusStateConnected) {
         return -1;
@@ -354,7 +354,7 @@ static bool xen_netdev_connect(XenDevice *xendev, Error **errp)
     XenNetDev *netdev = XEN_NET_DEVICE(xendev);
     unsigned int port, rx_copy;
 
-    assert(qemu_mutex_iothread_locked());
+    assert(bql_locked());
 
     if (xen_device_frontend_scanf(xendev, "tx-ring-ref", "%u",
                                   &netdev->tx_ring_ref) != 1) {
@@ -425,7 +425,7 @@ static void xen_netdev_disconnect(XenDevice *xendev, Error **errp)
 
     trace_xen_netdev_disconnect(netdev->dev);
 
-    assert(qemu_mutex_iothread_locked());
+    assert(bql_locked());
 
     netdev->tx_ring.sring = NULL;
     netdev->rx_ring.sring = NULL;
diff --git a/hw/ppc/pegasos2.c b/hw/ppc/pegasos2.c
index 3203a4a..d84f3f9 100644
--- a/hw/ppc/pegasos2.c
+++ b/hw/ppc/pegasos2.c
@@ -515,7 +515,7 @@ static void pegasos2_hypercall(PPCVirtualHypervisor *vhyp, PowerPCCPU *cpu)
     CPUPPCState *env = &cpu->env;
 
     /* The TCG path should also be holding the BQL at this point */
-    g_assert(qemu_mutex_iothread_locked());
+    g_assert(bql_locked());
 
     if (FIELD_EX64(env->msr, MSR, PR)) {
         qemu_log_mask(LOG_GUEST_ERROR, "Hypercall made with MSR[PR]=1\n");
diff --git a/hw/ppc/ppc.c b/hw/ppc/ppc.c
index c532d79..da1626f 100644
--- a/hw/ppc/ppc.c
+++ b/hw/ppc/ppc.c
@@ -314,7 +314,7 @@ void store_40x_dbcr0(CPUPPCState *env, uint32_t val)
 {
     PowerPCCPU *cpu = env_archcpu(env);
 
-    qemu_mutex_lock_iothread();
+    bql_lock();
 
     switch ((val >> 28) & 0x3) {
     case 0x0:
@@ -334,7 +334,7 @@ void store_40x_dbcr0(CPUPPCState *env, uint32_t val)
         break;
     }
 
-    qemu_mutex_unlock_iothread();
+    bql_unlock();
 }
 
 /* PowerPC 40x internal IRQ controller */
diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index 4997aa4..e8dabc8 100644
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -1304,7 +1304,7 @@ static void emulate_spapr_hypercall(PPCVirtualHypervisor *vhyp,
     CPUPPCState *env = &cpu->env;
 
     /* The TCG path should also be holding the BQL at this point */
-    g_assert(qemu_mutex_iothread_locked());
+    g_assert(bql_locked());
 
     g_assert(!vhyp_cpu_in_nested(cpu));
 
diff --git a/hw/ppc/spapr_rng.c b/hw/ppc/spapr_rng.c
index df5c4b9..c2fda7a 100644
--- a/hw/ppc/spapr_rng.c
+++ b/hw/ppc/spapr_rng.c
@@ -82,9 +82,9 @@ static target_ulong h_random(PowerPCCPU *cpu, SpaprMachineState *spapr,
     while (hrdata.received < 8) {
         rng_backend_request_entropy(rngstate->backend, 8 - hrdata.received,
                                     random_recv, &hrdata);
-        qemu_mutex_unlock_iothread();
+        bql_unlock();
         qemu_sem_wait(&hrdata.sem);
-        qemu_mutex_lock_iothread();
+        bql_lock();
     }
 
     qemu_sem_destroy(&hrdata.sem);
diff --git a/hw/ppc/spapr_softmmu.c b/hw/ppc/spapr_softmmu.c
index 2786663..fc1bbc0 100644
--- a/hw/ppc/spapr_softmmu.c
+++ b/hw/ppc/spapr_softmmu.c
@@ -334,7 +334,7 @@ static void *hpt_prepare_thread(void *opaque)
         pending->ret = H_NO_MEM;
     }
 
-    qemu_mutex_lock_iothread();
+    bql_lock();
 
     if (SPAPR_MACHINE(qdev_get_machine())->pending_hpt == pending) {
         /* Ready to go */
@@ -344,7 +344,7 @@ static void *hpt_prepare_thread(void *opaque)
         free_pending_hpt(pending);
     }
 
-    qemu_mutex_unlock_iothread();
+    bql_unlock();
     return NULL;
 }
 
diff --git a/hw/remote/mpqemu-link.c b/hw/remote/mpqemu-link.c
index 9bd98e8..d04ac93 100644
--- a/hw/remote/mpqemu-link.c
+++ b/hw/remote/mpqemu-link.c
@@ -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;
diff --git a/hw/remote/vfio-user-obj.c b/hw/remote/vfio-user-obj.c
index 8b10c32..d9b879e 100644
--- a/hw/remote/vfio-user-obj.c
+++ b/hw/remote/vfio-user-obj.c
@@ -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;
         }
 
diff --git a/hw/s390x/s390-skeys.c b/hw/s390x/s390-skeys.c
index 8f5159d..5c535d4 100644
--- a/hw/s390x/s390-skeys.c
+++ b/hw/s390x/s390-skeys.c
@@ -153,7 +153,7 @@ void qmp_dump_skeys(const char *filename, Error **errp)
         goto out;
     }
 
-    assert(qemu_mutex_iothread_locked());
+    assert(bql_locked());
     guest_phys_blocks_init(&guest_phys_blocks);
     guest_phys_blocks_append(&guest_phys_blocks);