diff options
| author | Paolo Bonzini <pbonzini@redhat.com> | 2016-09-02 23:33:38 +0200 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2016-09-27 11:57:30 +0200 |
| commit | 758e1b2b622d7c177dc2d95e887a11aa069b7e68 (patch) | |
| tree | 4b8fc6e2fa1fac81eeb8d038ee1f213dbab71a3a /cpus-common.c | |
| parent | cf07da65f335b9a74e62f5413078f67280572f36 (diff) | |
cpus-common: simplify locking for start_exclusive/end_exclusive
It is not necessary to hold qemu_cpu_list_mutex throughout the
exclusive section, because no other exclusive section can run
while pending_cpus != 0.
exclusive_idle() is called in cpu_exec_start(), and that prevents
any CPUs created after start_exclusive() from entering cpu_exec()
during an exclusive section.
Reviewed-by: Richard Henderson <rth@twiddle.net>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'cpus-common.c')
| -rw-r--r-- | cpus-common.c | 11 |
1 files changed, 8 insertions, 3 deletions
diff --git a/cpus-common.c b/cpus-common.c index 80aaf9b42d..429652c7fd 100644 --- a/cpus-common.c +++ b/cpus-common.c @@ -171,8 +171,7 @@ static inline void exclusive_idle(void) } /* Start an exclusive operation. - Must only be called from outside cpu_exec, takes - qemu_cpu_list_lock. */ + Must only be called from outside cpu_exec. */ void start_exclusive(void) { CPUState *other_cpu; @@ -191,11 +190,17 @@ void start_exclusive(void) while (pending_cpus > 1) { qemu_cond_wait(&exclusive_cond, &qemu_cpu_list_lock); } + + /* Can release mutex, no one will enter another exclusive + * section until end_exclusive resets pending_cpus to 0. + */ + qemu_mutex_unlock(&qemu_cpu_list_lock); } -/* Finish an exclusive operation. Releases qemu_cpu_list_lock. */ +/* Finish an exclusive operation. */ void end_exclusive(void) { + qemu_mutex_lock(&qemu_cpu_list_lock); pending_cpus = 0; qemu_cond_broadcast(&exclusive_resume); qemu_mutex_unlock(&qemu_cpu_list_lock); |