On 04/11/2020 15:17, Heikki Linnakangas wrote:
On 04/11/2020 14:03, Fujii Masao wrote:
Or ISTM that WakeupRecovery() should set the latch only when the latch
has not been reset to NULL yet.
Got to be careful with race conditions, if the latch is set to NULL at
the same time that WakeupRecovery() is called.
I don't think commit 113d3591b8 got this quite right:
void
WakeupRecovery(void)
{
if (XLogCtl->recoveryWakeupLatch)
SetLatch(XLogCtl->recoveryWakeupLatch);
}
If XLogCtl->recoveryWakeupLatch is set to NULL between the if and the
SetLatch, you'll still get a segfault. That's highly unlikely to happen
in practice because the compiler will optimize that into a single load
instruction, but could happen with -O0. I think you'd need to do the
access only once, using a volatile pointer, to make that safe. Maybe
it's simpler to just not reset it to NULL, after all.
- Heikki
