[Qemu-devel] [PATCH 0/2] IO-thread fixes

[Qemu-devel] [PATCH 0/2] IO-thread fixes

[Glauber Costa]

Builds ok, and does not offend anybody this time.

[Qemu-devel] [PATCH 1/2] unlock iothread mutex before running kvm ioctl

[Glauber Costa]

Without this, kvm will hold the mutex while it issues its run ioctl,
and never be able to step out of it, causing a deadlock.

Signed-off-by: Glauber Costa <glommer@redhat.com>
---
 kvm-all.c     |    2 ++
 qemu-common.h |    3 +++
 vl.c          |    8 ++++----
 3 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/kvm-all.c b/kvm-all.c
index 7dcc553..11f4414 100644
--- a/kvm-all.c
+++ b/kvm-all.c
@@ -605,7 +605,9 @@ int kvm_cpu_exec(CPUState *env)
         }
 
         kvm_arch_pre_run(env, run);
+        qemu_mutex_unlock_iothread();
         ret = kvm_vcpu_ioctl(env, KVM_RUN, 0);
+        qemu_mutex_lock_iothread();
         kvm_arch_post_run(env, run);
 
         if (ret == -EINTR || ret == -EAGAIN) {
diff --git a/qemu-common.h b/qemu-common.h
index 12e7dd0..820dd37 100644
--- a/qemu-common.h
+++ b/qemu-common.h
@@ -146,6 +146,9 @@ char *qemu_strndup(const char *str, size_t size);
 void *get_mmap_addr(unsigned long size);
 
 
+void qemu_mutex_lock_iothread(void);
+void qemu_mutex_unlock_iothread(void);
+
 /* Error handling.  */
 
 void QEMU_NORETURN hw_error(const char *fmt, ...)
diff --git a/vl.c b/vl.c
index eb01da7..3012141 100644
--- a/vl.c
+++ b/vl.c
@@ -3445,8 +3445,8 @@ void qemu_notify_event(void)
     }
 }
 
-#define qemu_mutex_lock_iothread() do { } while (0)
-#define qemu_mutex_unlock_iothread() do { } while (0)
+void qemu_mutex_lock_iothread(void) {}
+void qemu_mutex_unlock_iothread(void) {}
 
 void vm_stop(int reason)
 {
@@ -3640,7 +3640,7 @@ static void qemu_signal_lock(unsigned int msecs)
     qemu_mutex_unlock(&qemu_fair_mutex);
 }
 
-static void qemu_mutex_lock_iothread(void)
+void qemu_mutex_lock_iothread(void)
 {
     if (kvm_enabled()) {
         qemu_mutex_lock(&qemu_fair_mutex);
@@ -3650,7 +3650,7 @@ static void qemu_mutex_lock_iothread(void)
         qemu_signal_lock(100);
 }
 
-static void qemu_mutex_unlock_iothread(void)
+void qemu_mutex_unlock_iothread(void)
 {
     qemu_mutex_unlock(&qemu_global_mutex);
 }
-- 
1.6.2.5

[Qemu-devel] [PATCH 2/2] do proper cpu_self check

[Glauber Costa]

Currently, our check for qemu_cpu_self only checks if there is a cpu
currently in execution (represented by cpu_single_env being set). While
this might be okay for tcg, it is certainly not okay for kvm, since multiple
cpus might be executing.

Instead, I propose we use pthread primitives to test if the caller thread is
the same as env->thread.

For tcg, it will have the same semantics as before, since all CPUStates will
point to the same thread, and we'll only have one in execution at a time.

Signed-off-by: Glauber Costa <glommer@redhat.com>
---
 vl.c |    9 +++++++--
 1 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/vl.c b/vl.c
index 3012141..e141bd1 100644
--- a/vl.c
+++ b/vl.c
@@ -3582,9 +3582,14 @@ void qemu_cpu_kick(void *_env)
         qemu_thread_signal(env->thread, SIGUSR1);
 }
 
-int qemu_cpu_self(void *env)
+int qemu_cpu_self(void *_env)
 {
-    return (cpu_single_env != NULL);
+    CPUState *env = _env;
+    QemuThread this;
+ 
+    qemu_thread_self(&this);
+ 
+    return qemu_thread_equal(&this, env->thread);
 }
 
 static void cpu_signal(int sig)
-- 
1.6.2.5

[Qemu-devel] [PATCH 0/2] io-thread fixes

[Glauber Costa]

Hi,

Our iothread still does not work reliably, but with those fixes
I can get a little bit further.

Anthony, please let me know what you think of it.