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authorPaolo Bonzini <pbonzini@redhat.com>2016-08-31 21:33:58 +0200
committerPaolo Bonzini <pbonzini@redhat.com>2016-09-27 11:57:30 +0200
commitc265e976f4669fd65f5b47e6865f50d1cb66bd02 (patch)
treeb80f5c8500bd6ad92ee0474bce2b4186dd2540c5 /include/qom
parent3359baad36889b83df40b637ed993a4b816c4906 (diff)
cpus-common: lock-free fast path for cpu_exec_start/end
Set cpu->running without taking the cpu_list lock, only requiring it if there is a concurrent exclusive section. This requires adding a new field to CPUState, which records whether a running CPU is being counted in pending_cpus. When an exclusive section is started concurrently with cpu_exec_start, cpu_exec_start can use the new field to determine if it has to wait for the end of the exclusive section. Likewise, cpu_exec_end can use it to see if start_exclusive is waiting for that CPU. This a separate patch for easier bisection of issues. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'include/qom')
-rw-r--r--include/qom/cpu.h5
1 files changed, 3 insertions, 2 deletions
diff --git a/include/qom/cpu.h b/include/qom/cpu.h
index 5dfe74a0e7..22b54d6d93 100644
--- a/include/qom/cpu.h
+++ b/include/qom/cpu.h
@@ -242,7 +242,8 @@ struct qemu_work_item;
* @nr_threads: Number of threads within this CPU.
* @numa_node: NUMA node this CPU is belonging to.
* @host_tid: Host thread ID.
- * @running: #true if CPU is currently running;
+ * @running: #true if CPU is currently running (lockless).
+ * @has_waiter: #true if a CPU is currently waiting for the cpu_exec_end;
* valid under cpu_list_lock.
* @created: Indicates whether the CPU thread has been successfully created.
* @interrupt_request: Indicates a pending interrupt request.
@@ -296,7 +297,7 @@ struct CPUState {
#endif
int thread_id;
uint32_t host_tid;
- bool running;
+ bool running, has_waiter;
struct QemuCond *halt_cond;
bool thread_kicked;
bool created;