From 21618b3e55ad2c6fede0bffcaea466091811ce59 Mon Sep 17 00:00:00 2001 From: Paolo Bonzini Date: Fri, 27 Feb 2015 20:01:03 +0100 Subject: [PATCH] cpus: be more paranoid in avoiding deadlocks For good measure, ensure that the following sequence: thread 1 calls qemu_mutex_lock_iothread thread 2 calls qemu_mutex_lock_iothread VCPU thread are created VCPU thread enters execution loop results in the VCPU threads letting the other two threads run and obeying iothread_requesting_mutex even if the VCPUs are not halted. To do this, check iothread_requesting_mutex before execution starts. Tested-by: Leon Alrae Signed-off-by: Paolo Bonzini --- cpus.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/cpus.c b/cpus.c index 83c078e..0fac143 100644 --- a/cpus.c +++ b/cpus.c @@ -1025,6 +1025,9 @@ static void *qemu_tcg_cpu_thread_fn(void *arg) } } + /* process any pending work */ + exit_request = 1; + while (1) { tcg_exec_all(); @@ -1115,10 +1118,11 @@ bool qemu_in_vcpu_thread(void) void qemu_mutex_lock_iothread(void) { + atomic_inc(&iothread_requesting_mutex); if (!tcg_enabled() || !first_cpu) { qemu_mutex_lock(&qemu_global_mutex); + atomic_dec(&iothread_requesting_mutex); } else { - atomic_inc(&iothread_requesting_mutex); if (qemu_mutex_trylock(&qemu_global_mutex)) { qemu_cpu_kick_thread(first_cpu); qemu_mutex_lock(&qemu_global_mutex); -- 2.7.4