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[Qemu-devel] [PATCH v4 07/12] linux-user: Rework exclusive operation mec
From: |
Sergey Fedorov |
Subject: |
[Qemu-devel] [PATCH v4 07/12] linux-user: Rework exclusive operation mechanism |
Date: |
Fri, 15 Jul 2016 21:57:21 +0300 |
From: Sergey Fedorov <address@hidden>
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 <address@hidden>
Signed-off-by: Sergey Fedorov <address@hidden>
Reviewed-by: Alex Bennée <address@hidden>
---
Changes in v2:
- Rename 'tcg_pending_cpus' to 'tcg_pending_threads'
---
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 bdbda693cc5f..5ff0b20bad89 100644
--- a/linux-user/main.c
+++ b/linux-user/main.c
@@ -112,7 +112,8 @@ 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)
{
@@ -142,7 +143,8 @@ 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);
@@ -159,7 +161,7 @@ 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);
}
}
@@ -173,15 +175,14 @@ 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);
}
}
@@ -189,7 +190,7 @@ 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);
}
@@ -200,6 +201,7 @@ 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);
}
@@ -208,11 +210,9 @@ 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);
--
2.9.1
- [Qemu-devel] [PATCH v4 01/12] atomic: introduce atomic_dec_fetch., (continued)
- [Qemu-devel] [PATCH v4 01/12] atomic: introduce atomic_dec_fetch., Sergey Fedorov, 2016/07/15
- [Qemu-devel] [PATCH v4 11/12] cpu-exec-common: Introduce async_safe_run_on_cpu(), Sergey Fedorov, 2016/07/15
- [Qemu-devel] [PATCH v4 10/12] bsd-user: Support CPU work queue, Sergey Fedorov, 2016/07/15
- [Qemu-devel] [PATCH v4 05/12] cpus: Rename flush_queued_work(), Sergey Fedorov, 2016/07/15
- [Qemu-devel] [PATCH v4 06/12] linux-user: Use QemuMutex and QemuCond, Sergey Fedorov, 2016/07/15
- [Qemu-devel] [PATCH v4 02/12] cpus: pass CPUState to run_on_cpu helpers, Sergey Fedorov, 2016/07/15
- [Qemu-devel] [PATCH v4 08/12] linux-user: Add qemu_cpu_is_self() and qemu_cpu_kick(), Sergey Fedorov, 2016/07/15
- [Qemu-devel] [PATCH v4 03/12] cpus: Move common code out of {async_, }run_on_cpu(), Sergey Fedorov, 2016/07/15
- [Qemu-devel] [PATCH v4 12/12] tcg: Make tb_flush() thread safe, Sergey Fedorov, 2016/07/15
- [Qemu-devel] [PATCH v4 04/12] cpus: Wrap mutex used to protect CPU work, Sergey Fedorov, 2016/07/15
- [Qemu-devel] [PATCH v4 07/12] linux-user: Rework exclusive operation mechanism,
Sergey Fedorov <=
- [Qemu-devel] [PATCH v4 09/12] linux-user: Support CPU work queue, Sergey Fedorov, 2016/07/15