Jeff King <peff@xxxxxxxx> writes: >> One case I'd be worried about would be that the race is so bad that >> die-is-recursing-builtin never returns 0 even once. Everybody will >> just say "recursing" and die, without giving any useful information. > > I was trying to think how that would happen. If nobody's actually > recursing indefinitely, then the value in theory peaks at the number of > threads (modulo the fact that we're modifying a variable from multiple > threads without any locking; I'm not sure how reasonable it is to assume > in practice that sheared writes may cause us to lose an increment but > not to put nonsense in to the variable). If they are, then one thread > may increment it to 1024 before another thread gets a chance to say > anything. But in that case, the recursion-die is our expected outcome. > > Anyway, it might be reasonable to protect the counter with a mutex. > Like: > ... > To be honest, I'm not sure if it's worth giving it much more time, > though. I'd be fine with Ævar's patch as-is. The scenario I had in mind was three or more threads simultaneously dying, each incrementing dying counter by one and before any of them have a chance to say "called many times, error or racy threaded death!", because they all observe three (or more). But I was incorrectly reading the code---in that case, as long as dying is small enough, we'll return 0 and let at least one of the caller give a chance to give a message that came in "err" from their invocations of die()'s. So I do not think it is worth worrying about too deeply. Thanks.
