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Diffstat (limited to 'src/include/storage/latch.h')
| -rw-r--r-- | src/include/storage/latch.h | 16 |
1 files changed, 16 insertions, 0 deletions
diff --git a/src/include/storage/latch.h b/src/include/storage/latch.h index 28fc684d240..273836d5530 100644 --- a/src/include/storage/latch.h +++ b/src/include/storage/latch.h @@ -52,6 +52,22 @@ * do. Otherwise, if someone sets the latch between the check and the * ResetLatch call, you will miss it and Wait will incorrectly block. * + * Another valid coding pattern looks like: + * + * for (;;) + * { + * if (work to do) + * Do Stuff(); // in particular, exit loop if some condition satisfied + * WaitLatch(); + * ResetLatch(); + * } + * + * This is useful to reduce latch traffic if it's expected that the loop's + * termination condition will often be satisfied in the first iteration; + * the cost is an extra loop iteration before blocking when it is not. + * What must be avoided is placing any checks for asynchronous events after + * WaitLatch and before ResetLatch, as that creates a race condition. + * * To wake up the waiter, you must first set a global flag or something * else that the wait loop tests in the "if (work to do)" part, and call * SetLatch *after* that. SetLatch is designed to return quickly if the |