From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:49752) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bElDj-0005G3-QV for qemu-devel@nongnu.org; Sun, 19 Jun 2016 18:29:36 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1bElDh-0002LH-KF for qemu-devel@nongnu.org; Sun, 19 Jun 2016 18:29:34 -0400 Received: from mail-lf0-x236.google.com ([2a00:1450:4010:c07::236]:33879) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bElDh-0002KZ-7L for qemu-devel@nongnu.org; Sun, 19 Jun 2016 18:29:33 -0400 Received: by mail-lf0-x236.google.com with SMTP id h129so26380857lfh.1 for ; Sun, 19 Jun 2016 15:29:33 -0700 (PDT) From: Sergey Fedorov Date: Mon, 20 Jun 2016 01:28:29 +0300 Message-Id: <1466375313-7562-5-git-send-email-sergey.fedorov@linaro.org> In-Reply-To: <1466375313-7562-1-git-send-email-sergey.fedorov@linaro.org> References: <1466375313-7562-1-git-send-email-sergey.fedorov@linaro.org> Subject: [Qemu-devel] [RFC 4/8] linux-user: Rework exclusive operation mechanism List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: patches@linaro.org, Sergey Fedorov , Sergey Fedorov , Riku Voipio From: Sergey Fedorov A single variable 'pending_cpus' was used for both counting currently running CPUs and for signalling the pending exclusive operation request. To prepare for supporting operations which requires a quiescent state, like translation buffer flush, it is useful to keep a counter of currently running CPUs always up to date. Use a separate variable 'tcg_pending_cpus' to count for currently running CPUs and a separate variable 'exclusive_pending' to indicate that there's an exclusive operation pending. Signed-off-by: Sergey Fedorov Signed-off-by: Sergey Fedorov --- linux-user/main.c | 24 ++++++++++++------------ 1 file changed, 12 insertions(+), 12 deletions(-) diff --git a/linux-user/main.c b/linux-user/main.c index b9a4e0ea45ac..485336f78b8f 100644 --- a/linux-user/main.c +++ b/linux-user/main.c @@ -111,7 +111,8 @@ static pthread_mutex_t cpu_list_mutex = PTHREAD_MUTEX_INITIALIZER; static pthread_mutex_t exclusive_lock = PTHREAD_MUTEX_INITIALIZER; static pthread_cond_t exclusive_cond = PTHREAD_COND_INITIALIZER; static pthread_cond_t exclusive_resume = PTHREAD_COND_INITIALIZER; -static int pending_cpus; +static bool exclusive_pending; +static int tcg_pending_cpus; /* Make sure everything is in a consistent state for calling fork(). */ void fork_start(void) @@ -133,7 +134,8 @@ void fork_end(int child) QTAILQ_REMOVE(&cpus, cpu, node); } } - pending_cpus = 0; + tcg_pending_cpus = 0; + exclusive_pending = false; pthread_mutex_init(&exclusive_lock, NULL); pthread_mutex_init(&cpu_list_mutex, NULL); pthread_cond_init(&exclusive_cond, NULL); @@ -150,7 +152,7 @@ void fork_end(int child) must be held. */ static inline void exclusive_idle(void) { - while (pending_cpus) { + while (exclusive_pending) { pthread_cond_wait(&exclusive_resume, &exclusive_lock); } } @@ -164,15 +166,14 @@ static inline void start_exclusive(void) pthread_mutex_lock(&exclusive_lock); exclusive_idle(); - pending_cpus = 1; + exclusive_pending = true; /* Make all other cpus stop executing. */ CPU_FOREACH(other_cpu) { if (other_cpu->running) { - pending_cpus++; cpu_exit(other_cpu); } } - if (pending_cpus > 1) { + while (tcg_pending_cpus) { pthread_cond_wait(&exclusive_cond, &exclusive_lock); } } @@ -180,7 +181,7 @@ static inline void start_exclusive(void) /* Finish an exclusive operation. */ static inline void __attribute__((unused)) end_exclusive(void) { - pending_cpus = 0; + exclusive_pending = false; pthread_cond_broadcast(&exclusive_resume); pthread_mutex_unlock(&exclusive_lock); } @@ -191,6 +192,7 @@ static inline void cpu_exec_start(CPUState *cpu) pthread_mutex_lock(&exclusive_lock); exclusive_idle(); cpu->running = true; + tcg_pending_cpus++; pthread_mutex_unlock(&exclusive_lock); } @@ -199,11 +201,9 @@ static inline void cpu_exec_end(CPUState *cpu) { pthread_mutex_lock(&exclusive_lock); cpu->running = false; - if (pending_cpus > 1) { - pending_cpus--; - if (pending_cpus == 1) { - pthread_cond_signal(&exclusive_cond); - } + tcg_pending_cpus--; + if (!tcg_pending_cpus) { + pthread_cond_broadcast(&exclusive_cond); } exclusive_idle(); pthread_mutex_unlock(&exclusive_lock); -- 1.9.1