From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([209.51.188.92]:35027) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1goe35-0007sq-SO for qemu-devel@nongnu.org; Tue, 29 Jan 2019 19:48:17 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1goe34-0000dI-Gb for qemu-devel@nongnu.org; Tue, 29 Jan 2019 19:48:15 -0500 Received: from out1-smtp.messagingengine.com ([66.111.4.25]:53559) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1goe34-0000cu-CJ for qemu-devel@nongnu.org; Tue, 29 Jan 2019 19:48:14 -0500 From: "Emilio G. Cota" Date: Tue, 29 Jan 2019 19:47:02 -0500 Message-Id: <20190130004811.27372-5-cota@braap.org> In-Reply-To: <20190130004811.27372-1-cota@braap.org> References: <20190130004811.27372-1-cota@braap.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Subject: [Qemu-devel] [PATCH v6 04/73] cpu: make qemu_work_cond per-cpu List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: Richard Henderson , Paolo Bonzini This eliminates the need to use the BQL to queue CPU work. While at it, give the per-cpu field a generic name ("cond") since it will soon be used for more than just queueing CPU work. Reviewed-by: Richard Henderson Reviewed-by: Alex Bennée Signed-off-by: Emilio G. Cota --- include/qom/cpu.h | 6 ++-- cpus-common.c | 72 ++++++++++++++++++++++++++++++++++++++--------- cpus.c | 2 +- qom/cpu.c | 1 + 4 files changed, 63 insertions(+), 18 deletions(-) diff --git a/include/qom/cpu.h b/include/qom/cpu.h index 403c48695b..46e3c164aa 100644 --- a/include/qom/cpu.h +++ b/include/qom/cpu.h @@ -322,6 +322,7 @@ struct qemu_work_item; * @mem_io_vaddr: Target virtual address at which the memory was accessed. * @kvm_fd: vCPU file descriptor for KVM. * @lock: Lock to prevent multiple access to per-CPU fields. + * @cond: Condition variable for per-CPU events. * @work_list: List of pending asynchronous work. * @trace_dstate_delayed: Delayed changes to trace_dstate (includes all changes * to @trace_dstate). @@ -364,6 +365,7 @@ struct CPUState { QemuMutex lock; /* fields below protected by @lock */ + QemuCond cond; QSIMPLEQ_HEAD(, qemu_work_item) work_list; CPUAddressSpace *cpu_ases; @@ -771,12 +773,10 @@ bool cpu_is_stopped(CPUState *cpu); * @cpu: The vCPU to run on. * @func: The function to be executed. * @data: Data to pass to the function. - * @mutex: Mutex to release while waiting for @func to run. * * Used internally in the implementation of run_on_cpu. */ -void do_run_on_cpu(CPUState *cpu, run_on_cpu_func func, run_on_cpu_data data, - QemuMutex *mutex); +void do_run_on_cpu(CPUState *cpu, run_on_cpu_func func, run_on_cpu_data data); /** * run_on_cpu: diff --git a/cpus-common.c b/cpus-common.c index d0e619f149..daf1531868 100644 --- a/cpus-common.c +++ b/cpus-common.c @@ -26,7 +26,6 @@ static QemuMutex qemu_cpu_list_lock; static QemuCond exclusive_cond; static QemuCond exclusive_resume; -static QemuCond qemu_work_cond; /* >= 1 if a thread is inside start_exclusive/end_exclusive. Written * under qemu_cpu_list_lock, read with atomic operations. @@ -42,7 +41,6 @@ void qemu_init_cpu_list(void) qemu_mutex_init(&qemu_cpu_list_lock); qemu_cond_init(&exclusive_cond); qemu_cond_init(&exclusive_resume); - qemu_cond_init(&qemu_work_cond); } void cpu_list_lock(void) @@ -113,23 +111,37 @@ struct qemu_work_item { bool free, exclusive, done; }; -static void queue_work_on_cpu(CPUState *cpu, struct qemu_work_item *wi) +/* Called with the CPU's lock held */ +static void queue_work_on_cpu_locked(CPUState *cpu, struct qemu_work_item *wi) { - qemu_mutex_lock(&cpu->lock); QSIMPLEQ_INSERT_TAIL(&cpu->work_list, wi, node); wi->done = false; - qemu_mutex_unlock(&cpu->lock); qemu_cpu_kick(cpu); } -void do_run_on_cpu(CPUState *cpu, run_on_cpu_func func, run_on_cpu_data data, - QemuMutex *mutex) +static void queue_work_on_cpu(CPUState *cpu, struct qemu_work_item *wi) +{ + cpu_mutex_lock(cpu); + queue_work_on_cpu_locked(cpu, wi); + cpu_mutex_unlock(cpu); +} + +void do_run_on_cpu(CPUState *cpu, run_on_cpu_func func, run_on_cpu_data data) { struct qemu_work_item wi; + bool has_bql = qemu_mutex_iothread_locked(); + + g_assert(no_cpu_mutex_locked()); if (qemu_cpu_is_self(cpu)) { - func(cpu, data); + if (has_bql) { + func(cpu, data); + } else { + qemu_mutex_lock_iothread(); + func(cpu, data); + qemu_mutex_unlock_iothread(); + } return; } @@ -139,13 +151,34 @@ void do_run_on_cpu(CPUState *cpu, run_on_cpu_func func, run_on_cpu_data data, wi.free = false; wi.exclusive = false; - queue_work_on_cpu(cpu, &wi); + cpu_mutex_lock(cpu); + queue_work_on_cpu_locked(cpu, &wi); + + /* + * We are going to sleep on the CPU lock, so release the BQL. + * + * During the transition to per-CPU locks, we release the BQL _after_ + * having kicked the destination CPU (from queue_work_on_cpu_locked above). + * This makes sure that the enqueued work will be seen by the CPU + * after being woken up from the kick, since the CPU sleeps on the BQL. + * Once we complete the transition to per-CPU locks, we will release + * the BQL earlier in this function. + */ + if (has_bql) { + qemu_mutex_unlock_iothread(); + } + while (!atomic_mb_read(&wi.done)) { CPUState *self_cpu = current_cpu; - qemu_cond_wait(&qemu_work_cond, mutex); + qemu_cond_wait(&cpu->cond, &cpu->lock); current_cpu = self_cpu; } + cpu_mutex_unlock(cpu); + + if (has_bql) { + qemu_mutex_lock_iothread(); + } } void async_run_on_cpu(CPUState *cpu, run_on_cpu_func func, run_on_cpu_data data) @@ -307,6 +340,7 @@ void async_safe_run_on_cpu(CPUState *cpu, run_on_cpu_func func, void process_queued_cpu_work(CPUState *cpu) { struct qemu_work_item *wi; + bool has_bql = qemu_mutex_iothread_locked(); qemu_mutex_lock(&cpu->lock); if (QSIMPLEQ_EMPTY(&cpu->work_list)) { @@ -324,13 +358,23 @@ void process_queued_cpu_work(CPUState *cpu) * BQL, so it goes to sleep; start_exclusive() is sleeping too, so * neither CPU can proceed. */ - qemu_mutex_unlock_iothread(); + if (has_bql) { + qemu_mutex_unlock_iothread(); + } start_exclusive(); wi->func(cpu, wi->data); end_exclusive(); - qemu_mutex_lock_iothread(); + if (has_bql) { + qemu_mutex_lock_iothread(); + } } else { - wi->func(cpu, wi->data); + if (has_bql) { + wi->func(cpu, wi->data); + } else { + qemu_mutex_lock_iothread(); + wi->func(cpu, wi->data); + qemu_mutex_unlock_iothread(); + } } qemu_mutex_lock(&cpu->lock); if (wi->free) { @@ -340,5 +384,5 @@ void process_queued_cpu_work(CPUState *cpu) } } qemu_mutex_unlock(&cpu->lock); - qemu_cond_broadcast(&qemu_work_cond); + qemu_cond_broadcast(&cpu->cond); } diff --git a/cpus.c b/cpus.c index 187aed2533..42ea8cfbb5 100644 --- a/cpus.c +++ b/cpus.c @@ -1236,7 +1236,7 @@ void qemu_init_cpu_loop(void) void run_on_cpu(CPUState *cpu, run_on_cpu_func func, run_on_cpu_data data) { - do_run_on_cpu(cpu, func, data, &qemu_global_mutex); + do_run_on_cpu(cpu, func, data); } static void qemu_kvm_destroy_vcpu(CPUState *cpu) diff --git a/qom/cpu.c b/qom/cpu.c index a2964e53c6..be8393e589 100644 --- a/qom/cpu.c +++ b/qom/cpu.c @@ -372,6 +372,7 @@ static void cpu_common_initfn(Object *obj) cpu->nr_threads = 1; qemu_mutex_init(&cpu->lock); + qemu_cond_init(&cpu->cond); QSIMPLEQ_INIT(&cpu->work_list); QTAILQ_INIT(&cpu->breakpoints); QTAILQ_INIT(&cpu->watchpoints); -- 2.17.1