[Qemu-devel] [PATCH 7/8] timers: document (future) locking rules for icount

[Paolo Bonzini <pbonzini@redhat.com>]

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 cpus.c | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/cpus.c b/cpus.c
index 01acce2..bc675a4 100644
--- a/cpus.c
+++ b/cpus.c
@@ -98,17 +98,22 @@ static bool all_cpu_threads_idle(void)
 /***********************************************************/
 /* guest cycle counter */
 
+/* Protected by TimersState seqlock */
+
+/* Compensate for varying guest execution speed.  */
+static int64_t qemu_icount_bias;
+static int64_t vm_clock_warp_start;
 /* Conversion factor from emulated instructions to virtual clock ticks.  */
 static int icount_time_shift;
 /* Arbitrarily pick 1MIPS as the minimum allowable speed.  */
 #define MAX_ICOUNT_SHIFT 10
-/* Compensate for varying guest execution speed.  */
-static int64_t qemu_icount_bias;
+
+/* Only written by TCG thread */
+static int64_t qemu_icount;
+
 static QEMUTimer *icount_rt_timer;
 static QEMUTimer *icount_vm_timer;
 static QEMUTimer *icount_warp_timer;
-static int64_t vm_clock_warp_start;
-static int64_t qemu_icount;
 
 typedef struct TimersState {
     int64_t cpu_ticks_prev;
@@ -232,6 +237,8 @@ static void icount_adjust(void)
     int64_t cur_time;
     int64_t cur_icount;
     int64_t delta;
+
+    /* Protected by TimersState mutex.  */
     static int64_t last_delta;
 
     /* If the VM is not running, then do nothing.  */
-- 
1.8.3.1