diff options
Diffstat (limited to 'src/os_win/os_mtx_cond.c')
| -rw-r--r-- | src/os_win/os_mtx_cond.c | 43 |
1 files changed, 30 insertions, 13 deletions
diff --git a/src/os_win/os_mtx_cond.c b/src/os_win/os_mtx_cond.c index 79c62ccd7f2..0001c6c2322 100644 --- a/src/os_win/os_mtx_cond.c +++ b/src/os_win/os_mtx_cond.c @@ -13,8 +13,7 @@ * Allocate and initialize a condition variable. */ int -__wt_cond_alloc(WT_SESSION_IMPL *session, - const char *name, bool is_signalled, WT_CONDVAR **condp) +__wt_cond_alloc(WT_SESSION_IMPL *session, const char *name, WT_CONDVAR **condp) { WT_CONDVAR *cond; @@ -26,7 +25,7 @@ __wt_cond_alloc(WT_SESSION_IMPL *session, InitializeConditionVariable(&cond->cond); cond->name = name; - cond->waiters = is_signalled ? -1 : 0; + cond->waiters = 0; *condp = cond; return (0); @@ -38,8 +37,8 @@ __wt_cond_alloc(WT_SESSION_IMPL *session, * out period expires, let the caller know. */ void -__wt_cond_wait_signal( - WT_SESSION_IMPL *session, WT_CONDVAR *cond, uint64_t usecs, bool *signalled) +__wt_cond_wait_signal(WT_SESSION_IMPL *session, WT_CONDVAR *cond, + uint64_t usecs, bool (*run_func)(WT_SESSION_IMPL *), bool *signalled) { BOOL sleepret; DWORD milliseconds, windows_error; @@ -59,8 +58,26 @@ __wt_cond_wait_signal( EnterCriticalSection(&cond->mtx); locked = true; + /* + * It's possible to race with threads waking us up. That's not a problem + * if there are multiple wakeups because the next wakeup will get us, or + * if we're only pausing for a short period. It's a problem if there's + * only a single wakeup, our waker is likely waiting for us to exit. + * After acquiring the mutex (so we're guaranteed to be awakened by any + * future wakeup call), optionally check if we're OK to keep running. + * This won't ensure our caller won't just loop and call us again, but + * at least it's not our fault. + * + * Assert we're not waiting longer than a second if not checking the + * run status. + */ + WT_ASSERT(session, run_func != NULL || usecs <= WT_MILLION); + + if (run_func != NULL && !run_func(session)) + goto skipping; + if (usecs > 0) { - milliseconds64 = usecs / 1000; + milliseconds64 = usecs / WT_THOUSAND; /* * Check for 32-bit unsigned integer overflow @@ -90,7 +107,7 @@ __wt_cond_wait_signal( if (sleepret == 0) { windows_error = __wt_getlasterror(); if (windows_error == ERROR_TIMEOUT) { - *signalled = false; +skipping: *signalled = false; sleepret = 1; } } @@ -117,17 +134,17 @@ void __wt_cond_signal(WT_SESSION_IMPL *session, WT_CONDVAR *cond) { WT_DECL_RET; - bool locked; - - locked = false; __wt_verbose(session, WT_VERB_MUTEX, "signal %s", cond->name); /* - * Our callers are often setting flags to cause a thread to exit. Add - * a barrier to ensure the flags are seen by the threads. + * Our callers often set flags to cause a thread to exit. Add a barrier + * to ensure exit flags are seen by the sleeping threads, otherwise we + * can wake up a thread, it immediately goes back to sleep, and we'll + * hang. Use a full barrier (we may not write before waiting on thread + * join). */ - WT_WRITE_BARRIER(); + WT_FULL_BARRIER(); /* * Fast path if we are in (or can enter), a state where the next waiter |