Re: signalling a condvar from inside vs. signalling a condvar von outside

Am 23.04.2025 um 21:08 schrieb Chris M. Thomasson:

On 4/22/2025 10:13 PM, Bonita Montero wrote:

Am 22.04.2025 um 23:36 schrieb Chris M. Thomasson:
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It was created to try to _help_ with thundering herd. There can be some interesting issues... Think of pushing 12 items in the queue, broadcast inside the mutex, then 42 threads go onto the morph list. Depending on implementation, any new threads will not be able to acquire the mutex until those 42 threads are out of the morph. This can be bad for several reasons... If a thread is in the morph its in line waiting for it... So, it's a bit screwed and can't do anything else. If another thread can acquire the mutex before the morph is done, then it's basically thundering heard all over again. Fwiw, trying to scale mutexes is sort of odd anyway. We can make the best mutex ever, but they have trouble scaling.

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Do you have any source for your assumptions ?
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 For trying to scale mutexes? Look up clever mutex solutions vs, say, RCU. They bite the dust.

You make random asssumptions. I've measured that there's not
a thundering herd problem with condvars and glibc; look at the
parallel posting in this thread.