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authorPaolo Bonzini <pbonzini@redhat.com>2015-06-18 18:47:18 +0200
committerPaolo Bonzini <pbonzini@redhat.com>2015-07-01 15:45:50 +0200
commit2e7f7a3c86f884a77296a137b7c730a4d580c5c9 (patch)
treea6b808eefcf024455e90366c9ab77899167db614 /cpus.c
parentbdf026317daa3b9dfa281f29e96fbb6fd48394c8 (diff)
main-loop: use qemu_mutex_lock_iothread consistently
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 <fred.konrad@greensocs.com> Message-Id: <1434646046-27150-2-git-send-email-pbonzini@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'cpus.c')
-rw-r--r--cpus.c10
1 files changed, 7 insertions, 3 deletions
diff --git a/cpus.c b/cpus.c
index 4f0e54d53c..c09fbef5de 100644
--- a/cpus.c
+++ b/cpus.c
@@ -954,7 +954,7 @@ 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;
@@ -1034,10 +1034,10 @@ 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;
@@ -1149,7 +1149,11 @@ 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 {