From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:36514) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bUdTt-0008Fh-U2 for qemu-devel@nongnu.org; Tue, 02 Aug 2016 13:27:56 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1bUdTs-0002VB-QD for qemu-devel@nongnu.org; Tue, 02 Aug 2016 13:27:53 -0400 Received: from mail-wm0-x231.google.com ([2a00:1450:400c:c09::231]:35802) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bUdTs-0002Uq-FT for qemu-devel@nongnu.org; Tue, 02 Aug 2016 13:27:52 -0400 Received: by mail-wm0-x231.google.com with SMTP id f65so417908718wmi.0 for ; Tue, 02 Aug 2016 10:27:52 -0700 (PDT) From: =?UTF-8?q?Alex=20Benn=C3=A9e?= Date: Tue, 2 Aug 2016 18:27:38 +0100 Message-Id: <1470158864-17651-8-git-send-email-alex.bennee@linaro.org> In-Reply-To: <1470158864-17651-1-git-send-email-alex.bennee@linaro.org> References: <1470158864-17651-1-git-send-email-alex.bennee@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Subject: [Qemu-devel] [PATCH v5 07/13] linux-user: Rework exclusive operation mechanism List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: mttcg@listserver.greensocs.com, qemu-devel@nongnu.org, fred.konrad@greensocs.com, a.rigo@virtualopensystems.com, serge.fdrv@gmail.com, cota@braap.org, bobby.prani@gmail.com Cc: mark.burton@greensocs.com, pbonzini@redhat.com, jan.kiszka@siemens.com, rth@twiddle.net, peter.maydell@linaro.org, claudio.fontana@huawei.com, Sergey Fedorov , =?UTF-8?q?Alex=20Benn=C3=A9e?= , 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_threads' 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 Reviewed-by: Alex Bennée Signed-off-by: Alex Bennée --- 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 c80caeb..60ca69f 100644 --- a/linux-user/main.c +++ b/linux-user/main.c @@ -115,7 +115,8 @@ static QemuMutex cpu_list_mutex; static QemuMutex exclusive_lock; static QemuCond exclusive_cond; static QemuCond exclusive_resume; -static int pending_cpus; +static bool exclusive_pending; +static int tcg_pending_threads; void qemu_init_cpu_loop(void) { @@ -145,7 +146,8 @@ void fork_end(int child) QTAILQ_REMOVE(&cpus, cpu, node); } } - pending_cpus = 0; + tcg_pending_threads = 0; + exclusive_pending = false; qemu_mutex_init(&exclusive_lock); qemu_mutex_init(&cpu_list_mutex); qemu_cond_init(&exclusive_cond); @@ -162,7 +164,7 @@ void fork_end(int child) must be held. */ static inline void exclusive_idle(void) { - while (pending_cpus) { + while (exclusive_pending) { qemu_cond_wait(&exclusive_resume, &exclusive_lock); } } @@ -176,15 +178,14 @@ static inline void start_exclusive(void) qemu_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_threads) { qemu_cond_wait(&exclusive_cond, &exclusive_lock); } } @@ -192,7 +193,7 @@ static inline void start_exclusive(void) /* Finish an exclusive operation. */ static inline void __attribute__((unused)) end_exclusive(void) { - pending_cpus = 0; + exclusive_pending = false; qemu_cond_broadcast(&exclusive_resume); qemu_mutex_unlock(&exclusive_lock); } @@ -203,6 +204,7 @@ static inline void cpu_exec_start(CPUState *cpu) qemu_mutex_lock(&exclusive_lock); exclusive_idle(); cpu->running = true; + tcg_pending_threads++; qemu_mutex_unlock(&exclusive_lock); } @@ -211,11 +213,9 @@ static inline void cpu_exec_end(CPUState *cpu) { qemu_mutex_lock(&exclusive_lock); cpu->running = false; - if (pending_cpus > 1) { - pending_cpus--; - if (pending_cpus == 1) { - qemu_cond_signal(&exclusive_cond); - } + tcg_pending_threads--; + if (!tcg_pending_threads) { + qemu_cond_signal(&exclusive_cond); } exclusive_idle(); qemu_mutex_unlock(&exclusive_lock); -- 2.7.4