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[Qemu-devel] [PATCH 1/9] main-loop: use qemu_mutex_lock_iothread consist
From: |
Paolo Bonzini |
Subject: |
[Qemu-devel] [PATCH 1/9] main-loop: use qemu_mutex_lock_iothread consistently |
Date: |
Wed, 24 Jun 2015 18:25:02 +0200 |
The next patch will require the BQL to be always taken with
qemu_mutex_lock_iothread(), while right now this isn't the case.
Outside TCG mode this is not a problem. In TCG mode, we need to be
careful and avoid the "prod out of compiled code" step if already
in a VCPU thread. This is easily done with a check on current_cpu,
i.e. qemu_in_vcpu_thread().
Hopefully, multithreaded TCG will get rid of the whole logic to kick
VCPUs whenever an I/O event occurs!
Cc: Frederic Konrad <address@hidden>
Message-Id: <address@hidden>
Signed-off-by: Paolo Bonzini <address@hidden>
---
cpus.c | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)
diff --git a/cpus.c b/cpus.c
index b85fb5f..02cca5d 100644
--- a/cpus.c
+++ b/cpus.c
@@ -953,7 +953,7 @@ static void *qemu_kvm_cpu_thread_fn(void *arg)
CPUState *cpu = arg;
int r;
- qemu_mutex_lock(&qemu_global_mutex);
+ qemu_mutex_lock_iothread();
qemu_thread_get_self(cpu->thread);
cpu->thread_id = qemu_get_thread_id();
cpu->can_do_io = 1;
@@ -1033,10 +1033,10 @@ static void *qemu_tcg_cpu_thread_fn(void *arg)
{
CPUState *cpu = arg;
+ qemu_mutex_lock_iothread();
qemu_tcg_init_cpu_signals();
qemu_thread_get_self(cpu->thread);
- qemu_mutex_lock(&qemu_global_mutex);
CPU_FOREACH(cpu) {
cpu->thread_id = qemu_get_thread_id();
cpu->created = true;
@@ -1148,7 +1148,11 @@ bool qemu_in_vcpu_thread(void)
void qemu_mutex_lock_iothread(void)
{
atomic_inc(&iothread_requesting_mutex);
- if (!tcg_enabled() || !first_cpu || !first_cpu->thread) {
+ /* In the simple case there is no need to bump the VCPU thread out of
+ * TCG code execution.
+ */
+ if (!tcg_enabled() || qemu_in_vcpu_thread() ||
+ !first_cpu || !first_cpu->thread) {
qemu_mutex_lock(&qemu_global_mutex);
atomic_dec(&iothread_requesting_mutex);
} else {
--
1.8.3.1
- [Qemu-devel] [PATCH for-2.4 v2 0/9] KVM: Do I/O outside BQL whenever possible, Paolo Bonzini, 2015/06/24
- [Qemu-devel] [PATCH 3/9] memory: Add global-locking property to memory regions, Paolo Bonzini, 2015/06/24
- [Qemu-devel] [PATCH 4/9] exec: pull qemu_flush_coalesced_mmio_buffer() into address_space_rw/ld*/st*, Paolo Bonzini, 2015/06/24
- [Qemu-devel] [PATCH 1/9] main-loop: use qemu_mutex_lock_iothread consistently,
Paolo Bonzini <=
- [Qemu-devel] [PATCH 2/9] main-loop: introduce qemu_mutex_iothread_locked, Paolo Bonzini, 2015/06/24
- [Qemu-devel] [PATCH 5/9] memory: let address_space_rw/ld*/st* run outside the BQL, Paolo Bonzini, 2015/06/24
- [Qemu-devel] [PATCH 7/9] kvm: Switch to unlocked PIO, Paolo Bonzini, 2015/06/24
- [Qemu-devel] [PATCH 8/9] acpi: mark PMTIMER as unlocked, Paolo Bonzini, 2015/06/24
- [Qemu-devel] [PATCH 9/9] kvm: Switch to unlocked MMIO, Paolo Bonzini, 2015/06/24
- [Qemu-devel] [PATCH 6/9] kvm: First step to push iothread lock out of inner run loop, Paolo Bonzini, 2015/06/24