Mobile/Powersaving/Wakeups/Debugging

Finding Wakeups

One approach to finding wakeups is to add some debug prints to the relevant NSPR functions, which are PR_WaitCondVar (in nsprpub/pr/src/pthreads) and so forth, e.g.

PR_IMPLEMENT(PRStatus) PR_WaitCondVar(PRCondVar *cvar, PRIntervalTime timeout)
{
   printf("PR_WaitCondVar %x ; %d\n", cvar, timeout);

This can give you some useful information when running. To further detect what code is calling the function, consider running the debugger and placing breakpoints there, then looking at a stack trace.

Debugger tips:

• Placing a breakpoint in nsTimerImpl.cpp::Fire(), where it decides what callback to call ("switch (callbackType) {", currently line 425), can be very useful - simply step forward a little until you see what is being called.
• Note that working in the debugger, with freezing/continuing etc., will mess up the normal wakeup timing. So after discovering the relevant suspects using the debugger, consider adding debug printouts and running outside of the debugger to see which are actually more important in practice.

Current Wakeups of Notice

• 1 wakeup/sec: WatchdogMain runs JS_TriggerOperationCallback on all JS contexts, which is used for GC, infinite loop detection, etc.