diff options
| -rw-r--r-- | indra/test/sync.h | 51 |
1 files changed, 41 insertions, 10 deletions
diff --git a/indra/test/sync.h b/indra/test/sync.h index cafbc034b4..0f0b6cece8 100644 --- a/indra/test/sync.h +++ b/indra/test/sync.h @@ -41,18 +41,49 @@ public: mTimeout(timeout) {} - /// Bump mCond by n steps -- ideally, do this every time a participating - /// coroutine wakes up from any suspension. The choice to bump() after - /// resumption rather than just before suspending is worth calling out: - /// this practice relies on the fact that condition_variable::notify_all() - /// merely marks a suspended coroutine ready to run, rather than - /// immediately resuming it. This way, though, even if a coroutine exits - /// before reaching its next suspend point, the other coroutine isn't - /// left waiting forever. + /** + * Bump mCond by n steps -- ideally, do this every time a participating + * coroutine wakes up from any suspension. The choice to bump() after + * resumption rather than just before suspending is worth calling out: + * this practice relies on the fact that condition_variable::notify_all() + * merely marks a suspended coroutine ready to run, rather than + * immediately resuming it. This way, though, even if a coroutine exits + * before reaching its next suspend point, the other coroutine isn't + * left waiting forever. + */ void bump(int n=1) { - LL_DEBUGS() << llcoro::logname() << " bump(" << n << ") -> " << (mCond.get() + n) << LL_ENDL; - mCond.set_all(mCond.get() + n); + // Calling mCond.set_all(mCond.get() + n) would be great for + // coroutines -- but not so good between kernel threads -- it would be + // racy. Make the increment atomic by calling update_all(), which runs + // the passed lambda within a mutex lock. + int updated; + mCond.update_all( + [&n, &updated](int& data) + { + data += n; + // Capture the new value for possible logging purposes. + updated = data; + }); + // In the multi-threaded case, this log message could be a bit + // misleading, as it will be emitted after waiting threads have + // already awakened. But emitting the log message within the lock + // would seem to hold the lock longer than we really ought. + LL_DEBUGS() << llcoro::logname() << " bump(" << n << ") -> " << updated << LL_ENDL; + } + + /** + * Set mCond to a specific n. Use of bump() and yield() is nicely + * maintainable, since you can insert or delete matching operations in a + * test function and have the rest of the Sync operations continue to + * line up as before. But sometimes you need to get very specific, which + * is where set() and yield_until() come in handy: less maintainable, + * more precise. + */ + void set(int n) + { + LL_DEBUGS() << llcoro::logname() << " set(" << n << ")" << LL_ENDL; + mCond.set_all(n); } /// suspend until "somebody else" has bumped mCond by n steps |