From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:34564) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bly2p-0002Cd-C1 for qemu-devel@nongnu.org; Mon, 19 Sep 2016 08:51:43 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1bly2k-0001Gq-Dv for qemu-devel@nongnu.org; Mon, 19 Sep 2016 08:51:34 -0400 Received: from mx1.redhat.com ([209.132.183.28]:42654) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bly2k-0001Ga-4V for qemu-devel@nongnu.org; Mon, 19 Sep 2016 08:51:30 -0400 From: Paolo Bonzini Date: Mon, 19 Sep 2016 14:50:57 +0200 Message-Id: <1474289459-15242-15-git-send-email-pbonzini@redhat.com> In-Reply-To: <1474289459-15242-1-git-send-email-pbonzini@redhat.com> References: <1474289459-15242-1-git-send-email-pbonzini@redhat.com> Subject: [Qemu-devel] [PATCH 14/16] cpus-common: Introduce async_safe_run_on_cpu() List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: sergey.fedorov@linaro.org, serge.fdrv@gmail.com, alex.bennee@linaro.org We have to run safe work items outside the BQL; for now keep other work items within the BQL, though this can be changed relatively easily as a follow-up. Signed-off-by: Paolo Bonzini --- cpus-common.c | 33 +++++++++++++++++++++++++++++++-- include/qom/cpu.h | 14 ++++++++++++++ 2 files changed, 45 insertions(+), 2 deletions(-) diff --git a/cpus-common.c b/cpus-common.c index 6adc982..f7ad534 100644 --- a/cpus-common.c +++ b/cpus-common.c @@ -106,7 +106,7 @@ struct qemu_work_item { struct qemu_work_item *next; run_on_cpu_func func; void *data; - bool free, done; + bool free, exclusive, done; }; static void queue_work_on_cpu(CPUState *cpu, struct qemu_work_item *wi) @@ -139,6 +139,7 @@ void do_run_on_cpu(CPUState *cpu, run_on_cpu_func func, void *data, wi.data = data; wi.done = false; wi.free = false; + wi.exclusive = false; queue_work_on_cpu(cpu, &wi); while (!atomic_mb_read(&wi.done)) { @@ -157,6 +158,7 @@ void async_run_on_cpu(CPUState *cpu, run_on_cpu_func func, void *data) wi->func = func; wi->data = data; wi->free = true; + wi->exclusive = false; queue_work_on_cpu(cpu, wi); } @@ -230,6 +232,19 @@ void cpu_exec_end(CPUState *cpu) qemu_mutex_unlock(&qemu_cpu_list_mutex); } +void async_safe_run_on_cpu(CPUState *cpu, run_on_cpu_func func, void *data) +{ + struct qemu_work_item *wi; + + wi = g_malloc0(sizeof(struct qemu_work_item)); + wi->func = func; + wi->data = data; + wi->free = true; + wi->exclusive = true; + + queue_work_on_cpu(cpu, wi); +} + void process_queued_cpu_work(CPUState *cpu) { struct qemu_work_item *wi; @@ -246,7 +261,21 @@ void process_queued_cpu_work(CPUState *cpu) cpu->queued_work_last = NULL; } qemu_mutex_unlock(&cpu->work_mutex); - wi->func(cpu, wi->data); + if (wi->exclusive) { + /* Running work items outside the BQL avoids the following deadlock: + * 1) start_exclusive() is called with the BQL taken while another + * CPU is running; 2) cpu_exec in the other CPU tries to takes the + * BQL, so it goes to sleep; start_exclusive() is sleeping too, so + * neither CPU can proceed. + */ + qemu_mutex_unlock_iothread(); + start_exclusive(); + wi->func(cpu, wi->data); + end_exclusive(); + qemu_mutex_lock_iothread(); + } else { + wi->func(cpu, wi->data); + } qemu_mutex_lock(&cpu->work_mutex); if (wi->free) { g_free(wi); diff --git a/include/qom/cpu.h b/include/qom/cpu.h index 934c07a..4092dd9 100644 --- a/include/qom/cpu.h +++ b/include/qom/cpu.h @@ -656,6 +656,20 @@ void run_on_cpu(CPUState *cpu, run_on_cpu_func func, void *data); void async_run_on_cpu(CPUState *cpu, run_on_cpu_func func, void *data); /** + * async_safe_run_on_cpu: + * @cpu: The vCPU to run on. + * @func: The function to be executed. + * @data: Data to pass to the function. + * + * Schedules the function @func for execution on the vCPU @cpu asynchronously, + * while all other vCPUs are sleeping. + * + * Unlike run_on_cpu and async_run_on_cpu, the function is run outside the + * BQL. + */ +void async_safe_run_on_cpu(CPUState *cpu, run_on_cpu_func func, void *data); + +/** * qemu_get_cpu: * @index: The CPUState@cpu_index value of the CPU to obtain. * -- 2.7.4