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[Qemu-devel] [RFC 4/8] linux-user: Rework exclusive operation mechanism
From: |
Sergey Fedorov |
Subject: |
[Qemu-devel] [RFC 4/8] linux-user: Rework exclusive operation mechanism |
Date: |
Mon, 20 Jun 2016 01:28:29 +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_cpus' 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>
---
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 b9a4e0ea45ac..485336f78b8f 100644
--- a/linux-user/main.c
+++ b/linux-user/main.c
@@ -111,7 +111,8 @@ static pthread_mutex_t cpu_list_mutex =
PTHREAD_MUTEX_INITIALIZER;
static pthread_mutex_t exclusive_lock = PTHREAD_MUTEX_INITIALIZER;
static pthread_cond_t exclusive_cond = PTHREAD_COND_INITIALIZER;
static pthread_cond_t exclusive_resume = PTHREAD_COND_INITIALIZER;
-static int pending_cpus;
+static bool exclusive_pending;
+static int tcg_pending_cpus;
/* Make sure everything is in a consistent state for calling fork(). */
void fork_start(void)
@@ -133,7 +134,8 @@ void fork_end(int child)
QTAILQ_REMOVE(&cpus, cpu, node);
}
}
- pending_cpus = 0;
+ tcg_pending_cpus = 0;
+ exclusive_pending = false;
pthread_mutex_init(&exclusive_lock, NULL);
pthread_mutex_init(&cpu_list_mutex, NULL);
pthread_cond_init(&exclusive_cond, NULL);
@@ -150,7 +152,7 @@ void fork_end(int child)
must be held. */
static inline void exclusive_idle(void)
{
- while (pending_cpus) {
+ while (exclusive_pending) {
pthread_cond_wait(&exclusive_resume, &exclusive_lock);
}
}
@@ -164,15 +166,14 @@ static inline void start_exclusive(void)
pthread_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_cpus) {
pthread_cond_wait(&exclusive_cond, &exclusive_lock);
}
}
@@ -180,7 +181,7 @@ static inline void start_exclusive(void)
/* Finish an exclusive operation. */
static inline void __attribute__((unused)) end_exclusive(void)
{
- pending_cpus = 0;
+ exclusive_pending = false;
pthread_cond_broadcast(&exclusive_resume);
pthread_mutex_unlock(&exclusive_lock);
}
@@ -191,6 +192,7 @@ static inline void cpu_exec_start(CPUState *cpu)
pthread_mutex_lock(&exclusive_lock);
exclusive_idle();
cpu->running = true;
+ tcg_pending_cpus++;
pthread_mutex_unlock(&exclusive_lock);
}
@@ -199,11 +201,9 @@ static inline void cpu_exec_end(CPUState *cpu)
{
pthread_mutex_lock(&exclusive_lock);
cpu->running = false;
- if (pending_cpus > 1) {
- pending_cpus--;
- if (pending_cpus == 1) {
- pthread_cond_signal(&exclusive_cond);
- }
+ tcg_pending_cpus--;
+ if (!tcg_pending_cpus) {
+ pthread_cond_broadcast(&exclusive_cond);
}
exclusive_idle();
pthread_mutex_unlock(&exclusive_lock);
--
1.9.1
- [Qemu-devel] [RFC 0/8] cpu-exec: Safe work in quiescent state, Sergey Fedorov, 2016/06/19
- [Qemu-devel] [RFC 4/8] linux-user: Rework exclusive operation mechanism,
Sergey Fedorov <=
- [Qemu-devel] [RFC 5/8] linux-user: Add qemu_cpu_is_self() and qemu_cpu_kick(), Sergey Fedorov, 2016/06/19
- [Qemu-devel] [RFC 2/8] cpus: Move common code out of {async_, }run_on_cpu(), Sergey Fedorov, 2016/06/19
- [Qemu-devel] [RFC 1/8] cpus: pass CPUState to run_on_cpu helpers, Sergey Fedorov, 2016/06/19
- [Qemu-devel] [RFC 3/8] cpus: Add 'qemu_work_cond' usage wrappers, Sergey Fedorov, 2016/06/19