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Upstream-Status: Submitted
From f354b9333408d411854af058cc44cceda60b4473 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?An=C3=ADbal=20Lim=C3=B3n?= <anibal.limon@linux.intel.com>
Date: Thu, 3 Sep 2015 14:07:34 -0500
Subject: [PATCH] cpus.c: qemu_mutex_lock_iothread fix race condition at cpu
thread init
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
When QEMU starts the RCU thread executes qemu_mutex_lock_thread
causing error "qemu:qemu_cpu_kick_thread: No such process" and exits.
This isn't occur frequently but in glibc the thread id can exist and
this not guarantee that the thread is on active/running state. If is
inserted a sleep(1) after newthread assignment [1] the issue appears.
So not make assumption that thread exist if first_cpu->thread is set
then change the validation of cpu to created that is set into cpu
threads (kvm, tcg, dummy).
[1] https://sourceware.org/git/?p=glibc.git;a=blob;f=nptl/pthread_create.c;h=d10f4ea8004e1d8f3a268b95cc0f8d93b8d89867;hb=HEAD#l621
Signed-off-by: Aníbal Limón <anibal.limon@linux.intel.com>
---
cpus.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/cpus.c b/cpus.c
index 7e4786e..05e5400 100644
--- a/cpus.c
+++ b/cpus.c
@@ -1171,7 +1171,7 @@ void qemu_mutex_lock_iothread(void)
* TCG code execution.
*/
if (!tcg_enabled() || qemu_in_vcpu_thread() ||
- !first_cpu || !first_cpu->thread) {
+ !first_cpu || !first_cpu->created) {
qemu_mutex_lock(&qemu_global_mutex);
atomic_dec(&iothread_requesting_mutex);
} else {
--
1.9.1
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