From: Nikhil Mahale <[email protected]>
Fixing following kind of race-conditions -
WaitForSomething()
|
----> // timers -> timer-1 -> timer-2 -> null
while (timers && (int) (timers->expires - now) <= 0)
// prototype - DoTimer(OsTimerPtr timer, CARD32 now, OsTimerPtr
*prev)
DoTimer(timers, now, &timers)
|
|
----> OsBlockSignals(); .... OS Signal comes just before
blocking it,
.... timer-1 handler gets called.
// timer-1 gets served and
scheduled again;
// timers -> timer-2 -> timer-1 ->
null
....
*prev = timer->next;
timer->next = NULL; // timers -> null
// timers list gets corrupted here and timer-2 gets
removed from list.
Fixes: https://bugs.freedesktop.org/show_bug.cgi?id=86288
Signed-off-by: Nikhil Mahale <[email protected]>
Reviewed-by: Julien Cristau <[email protected]>
v2: Apply warning fixes from Keith Packard <[email protected]>
Reviewed-by: Aaron Plattner <[email protected]>
Signed-off-by: Aaron Plattner <[email protected]>
---
os/WaitFor.c | 41 ++++++++++++++++++++++++++---------------
1 file changed, 26 insertions(+), 15 deletions(-)
diff --git a/os/WaitFor.c b/os/WaitFor.c
index 86d96c846baa..431f1a6b6e7c 100644
--- a/os/WaitFor.c
+++ b/os/WaitFor.c
@@ -121,9 +121,9 @@ struct _OsTimerRec {
void *arg;
};
-static void DoTimer(OsTimerPtr timer, CARD32 now, OsTimerPtr *prev);
+static void DoTimer(OsTimerPtr timer, CARD32 now, volatile OsTimerPtr *prev);
static void CheckAllTimers(void);
-static OsTimerPtr timers = NULL;
+static volatile OsTimerPtr timers = NULL;
/*****************
* WaitForSomething:
@@ -263,11 +263,14 @@ WaitForSomething(int *pClientsReady)
if ((int) (timers->expires - now) <= 0)
expired = 1;
- while (timers && (int) (timers->expires - now) <= 0)
- DoTimer(timers, now, &timers);
+ if (expired) {
+ OsBlockSignals();
+ while (timers && (int) (timers->expires - now) <= 0)
+ DoTimer(timers, now, &timers);
+ OsReleaseSignals();
- if (expired)
return 0;
+ }
}
}
else {
@@ -281,11 +284,14 @@ WaitForSomething(int *pClientsReady)
if ((int) (timers->expires - now) <= 0)
expired = 1;
- while (timers && (int) (timers->expires - now) <= 0)
- DoTimer(timers, now, &timers);
+ if (expired) {
+ OsBlockSignals();
+ while (timers && (int) (timers->expires - now) <= 0)
+ DoTimer(timers, now, &timers);
+ OsReleaseSignals();
- if (expired)
return 0;
+ }
}
}
if (someReady)
@@ -401,24 +407,25 @@ CheckAllTimers(void)
}
static void
-DoTimer(OsTimerPtr timer, CARD32 now, OsTimerPtr *prev)
+DoTimer(OsTimerPtr timer, CARD32 now, volatile OsTimerPtr *prev)
{
CARD32 newTime;
OsBlockSignals();
*prev = timer->next;
timer->next = NULL;
+ OsReleaseSignals();
+
newTime = (*timer->callback) (timer, now, timer->arg);
if (newTime)
TimerSet(timer, 0, newTime, timer->callback, timer->arg);
- OsReleaseSignals();
}
OsTimerPtr
TimerSet(OsTimerPtr timer, int flags, CARD32 millis,
OsTimerCallback func, void *arg)
{
- register OsTimerPtr *prev;
+ volatile OsTimerPtr *prev;
CARD32 now = GetTimeInMillis();
if (!timer) {
@@ -470,7 +477,7 @@ Bool
TimerForce(OsTimerPtr timer)
{
int rc = FALSE;
- OsTimerPtr *prev;
+ volatile OsTimerPtr *prev;
OsBlockSignals();
for (prev = &timers; *prev; prev = &(*prev)->next) {
@@ -487,7 +494,7 @@ TimerForce(OsTimerPtr timer)
void
TimerCancel(OsTimerPtr timer)
{
- OsTimerPtr *prev;
+ volatile OsTimerPtr *prev;
if (!timer)
return;
@@ -515,8 +522,12 @@ TimerCheck(void)
{
CARD32 now = GetTimeInMillis();
- while (timers && (int) (timers->expires - now) <= 0)
- DoTimer(timers, now, &timers);
+ if (timers && (int) (timers->expires - now) <= 0) {
+ OsBlockSignals();
+ while (timers && (int) (timers->expires - now) <= 0)
+ DoTimer(timers, now, &timers);
+ OsReleaseSignals();
+ }
}
void
--
2.2.2
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