[Qemu-devel] [PATCH 6/6] qemu-timer: Fix limits for w32 mmtimer

[Stefan Weil <sw@weilnetz.de>]

timeSetEvent only accepts delays in the range which is returned by
timeGetDevCaps.

The lower limit is typically 1 (= 1 ms), so the constant value of 1
in the old code usually worked.

The upper limit can be as low as 10000 ms, so the latest changes in
QEMU's timer handling which introduced timeout values above that limit
could result in failures of timeSetEvent when the timer was re-armed.

Signed-off-by: Stefan Weil <sw@weilnetz.de>
---
 qemu-timer.c |   34 ++++++++++++++--------------------
 1 files changed, 14 insertions(+), 20 deletions(-)

diff --git a/qemu-timer.c b/qemu-timer.c
index 8eadd16..b9fd75d 100644
--- a/qemu-timer.c
+++ b/qemu-timer.c
@@ -611,7 +611,7 @@ static void unix_stop_timer(struct qemu_alarm_timer *t)
 #ifdef _WIN32
 
 static MMRESULT mm_timer;
-static unsigned mm_period;
+static TIMECAPS mm_tc;
 
 static void CALLBACK mm_alarm_handler(UINT uTimerID, UINT uMsg,
                                       DWORD_PTR dwUser, DWORD_PTR dw1,
@@ -628,16 +628,12 @@ static void CALLBACK mm_alarm_handler(UINT uTimerID, UINT uMsg,
 
 static int mm_start_timer(struct qemu_alarm_timer *t)
 {
-    TIMECAPS tc;
+    timeGetDevCaps(&mm_tc, sizeof(mm_tc));
 
-    memset(&tc, 0, sizeof(tc));
-    timeGetDevCaps(&tc, sizeof(tc));
+    timeBeginPeriod(mm_tc.wPeriodMin);
 
-    mm_period = tc.wPeriodMin;
-    timeBeginPeriod(mm_period);
-
-    mm_timer = timeSetEvent(1,                  /* interval (ms) */
-                            mm_period,          /* resolution */
+    mm_timer = timeSetEvent(mm_tc.wPeriodMin,   /* interval (ms) */
+                            mm_tc.wPeriodMin,   /* resolution */
                             mm_alarm_handler,   /* function */
                             (DWORD_PTR)t,       /* parameter */
                             TIME_ONESHOT | TIME_CALLBACK_FUNCTION);
@@ -645,7 +641,7 @@ static int mm_start_timer(struct qemu_alarm_timer *t)
     if (!mm_timer) {
         fprintf(stderr, "Failed to initialize win32 alarm timer: %ld\n",
                 GetLastError());
-        timeEndPeriod(mm_period);
+        timeEndPeriod(mm_tc.wPeriodMin);
         return -1;
     }
 
@@ -655,23 +651,21 @@ static int mm_start_timer(struct qemu_alarm_timer *t)
 static void mm_stop_timer(struct qemu_alarm_timer *t)
 {
     timeKillEvent(mm_timer);
-    timeEndPeriod(mm_period);
+    timeEndPeriod(mm_tc.wPeriodMin);
 }
 
 static void mm_rearm_timer(struct qemu_alarm_timer *t, int64_t delta)
 {
     int64_t nearest_delta_ms = delta / 1000000;
-    if (nearest_delta_ms < 1) {
-        nearest_delta_ms = 1;
-    }
-    /* UINT_MAX can be 32 bit */
-    if (nearest_delta_ms > UINT_MAX) {
-        nearest_delta_ms = UINT_MAX;
+    if (nearest_delta_ms < mm_tc.wPeriodMin) {
+        nearest_delta_ms = mm_tc.wPeriodMin;
+    } else if (nearest_delta_ms > mm_tc.wPeriodMax) {
+        nearest_delta_ms = mm_tc.wPeriodMax;
     }
 
     timeKillEvent(mm_timer);
-    mm_timer = timeSetEvent((unsigned int) nearest_delta_ms,
-                            mm_period,
+    mm_timer = timeSetEvent((UINT)nearest_delta_ms,
+                            mm_tc.wPeriodMin,
                             mm_alarm_handler,
                             (DWORD_PTR)t,
                             TIME_ONESHOT | TIME_CALLBACK_FUNCTION);
@@ -680,7 +674,7 @@ static void mm_rearm_timer(struct qemu_alarm_timer *t, int64_t delta)
         fprintf(stderr, "Failed to re-arm win32 alarm timer %ld\n",
                 GetLastError());
 
-        timeEndPeriod(mm_period);
+        timeEndPeriod(mm_tc.wPeriodMin);
         exit(1);
     }
 }
-- 
1.7.9