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From: Robert Foley <robert.foley@linaro.org>
To: qemu-devel@nongnu.org
Cc: richard.henderson@linaro.org, "Emilio G. Cota" <cota@braap.org>,
	alex.bennee@linaro.org, robert.foley@linaro.org,
	peter.puhov@linaro.org
Subject: [PATCH v8 04/74] cpu: make qemu_work_cond per-cpu
Date: Thu, 26 Mar 2020 15:30:46 -0400
Message-ID: <20200326193156.4322-5-robert.foley@linaro.org> (raw)
In-Reply-To: <20200326193156.4322-1-robert.foley@linaro.org>

From: "Emilio G. Cota" <cota@braap.org>

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 <richard.henderson@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Emilio G. Cota <cota@braap.org>
Signed-off-by: Robert Foley <robert.foley@linaro.org>
---
 cpus-common.c         | 72 ++++++++++++++++++++++++++++++++++---------
 cpus.c                |  2 +-
 hw/core/cpu.c         |  1 +
 include/hw/core/cpu.h |  6 ++--
 4 files changed, 63 insertions(+), 18 deletions(-)

diff --git a/cpus-common.c b/cpus-common.c
index f75cae23d9..9031c31005 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)
@@ -105,23 +103,37 @@ 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;
     }
 
@@ -131,13 +143,34 @@ 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)
@@ -303,6 +336,7 @@ 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)) {
@@ -320,13 +354,23 @@ 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) {
@@ -336,5 +380,5 @@ 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 633734fb5c..e1f3327bbc 100644
--- a/cpus.c
+++ b/cpus.c
@@ -1191,7 +1191,7 @@ 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/hw/core/cpu.c b/hw/core/cpu.c
index bc0416829a..6594323d77 100644
--- a/hw/core/cpu.c
+++ b/hw/core/cpu.c
@@ -368,6 +368,7 @@ 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);
diff --git a/include/hw/core/cpu.h b/include/hw/core/cpu.h
index 4521bba7a5..9c3ec715e2 100644
--- a/include/hw/core/cpu.h
+++ b/include/hw/core/cpu.h
@@ -333,6 +333,7 @@ struct qemu_work_item;
  * @kvm_fd: vCPU file descriptor for KVM.
  * @lock: Lock to prevent multiple access to per-CPU fields. Must be acquired
  *        after the BQL.
+ * @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).
@@ -378,6 +379,7 @@ struct CPUState {
 
     QemuMutex lock;
     /* fields below protected by @lock */
+    QemuCond cond;
     QSIMPLEQ_HEAD(, qemu_work_item) work_list;
 
     CPUAddressSpace *cpu_ases;
@@ -769,12 +771,10 @@ 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:
-- 
2.17.1



  parent reply index

Thread overview: 100+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-26 19:30 [PATCH v8 00/74] per-CPU locks Robert Foley
2020-03-26 19:30 ` [PATCH v8 01/74] cpu: convert queued work to a QSIMPLEQ Robert Foley
2020-03-26 19:30 ` [PATCH v8 02/74] cpu: rename cpu->work_mutex to cpu->lock Robert Foley
2020-05-11 14:48   ` Alex Bennée
2020-05-11 16:33     ` Robert Foley
2020-03-26 19:30 ` [PATCH v8 03/74] cpu: introduce cpu_mutex_lock/unlock Robert Foley
2020-05-11 10:24   ` Alex Bennée
2020-05-11 16:09     ` Robert Foley
2020-03-26 19:30 ` Robert Foley [this message]
2020-03-26 19:30 ` [PATCH v8 05/74] cpu: move run_on_cpu to cpus-common Robert Foley
2020-03-26 19:30 ` [PATCH v8 06/74] cpu: introduce process_queued_cpu_work_locked Robert Foley
2020-03-26 19:30 ` [PATCH v8 07/74] cpu: make per-CPU locks an alias of the BQL in TCG rr mode Robert Foley
2020-03-26 19:30 ` [PATCH v8 08/74] tcg-runtime: define helper_cpu_halted_set Robert Foley
2020-03-26 19:30 ` [PATCH v8 09/74] ppc: convert to helper_cpu_halted_set Robert Foley
2020-03-26 19:30 ` [PATCH v8 10/74] cris: " Robert Foley
2020-03-26 19:30 ` [PATCH v8 11/74] hppa: " Robert Foley
2020-03-26 19:30 ` [PATCH v8 12/74] m68k: " Robert Foley
2020-03-26 19:30 ` [PATCH v8 13/74] alpha: " Robert Foley
2020-03-26 19:30 ` [PATCH v8 14/74] microblaze: " Robert Foley
2020-03-26 19:30 ` [PATCH v8 15/74] cpu: define cpu_halted helpers Robert Foley
2020-03-26 19:30 ` [PATCH v8 16/74] tcg-runtime: convert to cpu_halted_set Robert Foley
2020-03-26 19:30 ` [PATCH v8 17/74] hw/semihosting: " Robert Foley
2020-05-11 10:25   ` Alex Bennée
2020-03-26 19:31 ` [PATCH v8 18/74] arm: convert to cpu_halted Robert Foley
2020-03-26 19:31 ` [PATCH v8 19/74] ppc: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 20/74] sh4: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 21/74] i386: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 22/74] lm32: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 23/74] m68k: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 24/74] mips: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 25/74] riscv: " Robert Foley
2020-05-11 10:40   ` Alex Bennée
2020-05-11 16:13     ` Robert Foley
2020-03-26 19:31 ` [PATCH v8 26/74] s390x: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 27/74] sparc: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 28/74] xtensa: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 29/74] gdbstub: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 30/74] openrisc: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 31/74] cpu-exec: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 32/74] cpu: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 33/74] cpu: define cpu_interrupt_request helpers Robert Foley
2020-03-26 19:31 ` [PATCH v8 34/74] ppc: use cpu_reset_interrupt Robert Foley
2020-03-26 19:31 ` [PATCH v8 35/74] exec: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 36/74] i386: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 37/74] s390x: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 38/74] openrisc: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 39/74] arm: convert to cpu_interrupt_request Robert Foley
2020-03-26 19:31 ` [PATCH v8 40/74] i386: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 41/74] i386/kvm: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 42/74] i386/hax-all: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 43/74] i386/whpx-all: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 44/74] i386/hvf: convert to cpu_request_interrupt Robert Foley
2020-03-26 19:31 ` [PATCH v8 45/74] ppc: convert to cpu_interrupt_request Robert Foley
2020-03-26 19:31 ` [PATCH v8 46/74] sh4: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 47/74] cris: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 48/74] hppa: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 49/74] lm32: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 50/74] m68k: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 51/74] mips: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 52/74] nios: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 53/74] s390x: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 54/74] alpha: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 55/74] moxie: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 56/74] sparc: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 57/74] openrisc: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 58/74] unicore32: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 59/74] microblaze: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 60/74] accel/tcg: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 61/74] cpu: convert to interrupt_request Robert Foley
2020-03-26 19:31 ` [PATCH v8 62/74] cpu: call .cpu_has_work with the CPU lock held Robert Foley
2020-03-26 19:31 ` [PATCH v8 63/74] cpu: introduce cpu_has_work_with_iothread_lock Robert Foley
2020-03-26 19:31 ` [PATCH v8 64/74] ppc: convert to cpu_has_work_with_iothread_lock Robert Foley
2020-03-26 19:31 ` [PATCH v8 65/74] mips: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 66/74] s390x: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 67/74] riscv: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 68/74] sparc: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 69/74] xtensa: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 70/74] cpu: rename all_cpu_threads_idle to qemu_tcg_rr_all_cpu_threads_idle Robert Foley
2020-03-26 19:31 ` [PATCH v8 71/74] cpu: protect CPU state with cpu->lock instead of the BQL Robert Foley
2020-03-26 19:31 ` [PATCH v8 72/74] cpus-common: release BQL earlier in run_on_cpu Robert Foley
2020-03-26 19:31 ` [PATCH v8 73/74] cpu: add async_run_on_cpu_no_bql Robert Foley
2020-03-26 19:31 ` [PATCH v8 74/74] cputlb: queue async flush jobs without the BQL Robert Foley
2020-05-12 16:27   ` Alex Bennée
2020-05-12 19:26     ` Robert Foley
2020-05-18 13:46       ` Robert Foley
2020-05-20  4:46         ` Emilio G. Cota
2020-05-20 15:01           ` Robert Foley
2020-05-21 14:17             ` Robert Foley
2020-05-12 18:38   ` Alex Bennée
2020-03-26 22:58 ` [PATCH v8 00/74] per-CPU locks Aleksandar Markovic
2020-03-27  9:39   ` Alex Bennée
2020-03-27  9:50     ` Aleksandar Markovic
2020-03-27 10:24       ` Aleksandar Markovic
2020-03-27 17:21         ` Robert Foley
2020-03-27  5:14 ` Emilio G. Cota
2020-03-27 10:59   ` Philippe Mathieu-Daudé
2020-03-30  8:57     ` Stefan Hajnoczi
2020-03-27 18:23   ` Alex Bennée
2020-03-27 18:30   ` Robert Foley
2020-05-12 16:29 ` Alex Bennée

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