Date: Thu, 14 Feb 2019 18:19:36 -0500 From: Rich Felker <dalias@...c.org> To: Alexey Izbyshev <izbyshev@...ras.ru> Cc: musl@...ts.openwall.com Subject: Re: Draft outline of thread-list design On Thu, Feb 14, 2019 at 05:32:24PM -0500, Rich Felker wrote: > On Fri, Feb 15, 2019 at 12:16:39AM +0300, Alexey Izbyshev wrote: > > In general, to my limited expertise, the design looks simple and > > clean. I'm not sure whether it's worth optimizing to reduce > > serialization pressure on pthread_create()/pthread_exit() because > > creating a large amount of short-lived threads doesn't look like a > > good idea anyway. > > Yes. One thing I did notice is that the window where pthread_create > has to hold a lock to prevent new dlopen from happening is a lot > larger than the window where the thread list needs to be locked, and > contains mmap/mprotect. I think we should add a new "DTLS lock" here > that's held for the whole time, with a protocol that if you need both > the DTLS lock and the thread list lock, you take them in that order > (dlopen would also need them both). This reduces the thread list lock > window to just the __clone call and list update. Also: the DTLS lock function can have a weak dummy, so that static-linked programs don't even perform any locking. Rich
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