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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>
This commit is contained in:
Paolo Bonzini 2015-06-18 18:47:18 +02:00
parent bdf026317d
commit 2e7f7a3c86
1 changed files with 7 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
cpus.c
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@ -954,7 +954,7 @@ static void *qemu_kvm_cpu_thread_fn(void *arg)
CPUState *cpu = arg; CPUState *cpu = arg;
int r; int r;
qemu_mutex_lock(&qemu_global_mutex); qemu_mutex_lock_iothread();
qemu_thread_get_self(cpu->thread); qemu_thread_get_self(cpu->thread);
cpu->thread_id = qemu_get_thread_id(); cpu->thread_id = qemu_get_thread_id();
cpu->can_do_io = 1; cpu->can_do_io = 1;
@ -1034,10 +1034,10 @@ static void *qemu_tcg_cpu_thread_fn(void *arg)
{ {
CPUState *cpu = arg; CPUState *cpu = arg;
qemu_mutex_lock_iothread();
qemu_tcg_init_cpu_signals(); qemu_tcg_init_cpu_signals();
qemu_thread_get_self(cpu->thread); qemu_thread_get_self(cpu->thread);
qemu_mutex_lock(&qemu_global_mutex);
CPU_FOREACH(cpu) { CPU_FOREACH(cpu) {
cpu->thread_id = qemu_get_thread_id(); cpu->thread_id = qemu_get_thread_id();
cpu->created = true; cpu->created = true;
@ -1149,7 +1149,11 @@ bool qemu_in_vcpu_thread(void)
void qemu_mutex_lock_iothread(void) void qemu_mutex_lock_iothread(void)
{ {
atomic_inc(&iothread_requesting_mutex); 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); qemu_mutex_lock(&qemu_global_mutex);
atomic_dec(&iothread_requesting_mutex); atomic_dec(&iothread_requesting_mutex);
} else { } else {