[Bug 259076] pthread_mutex_init fails with limited AS

From: <bugzilla-noreply_at_freebsd.org>
Date: Mon, 11 Oct 2021 15:59:11 UTC

            Bug ID: 259076
           Summary: pthread_mutex_init fails with limited AS
           Product: Base System
           Version: CURRENT
          Hardware: Any
                OS: Any
            Status: New
          Severity: Affects Some People
          Priority: ---
         Component: misc
          Assignee: bugs@FreeBSD.org
          Reporter: dynamic-wind@mail.ru

A complex application run in limited address space eventually fails to allocate
a mutex.
pthread_mutex_init normally calls __thr_calloc which calls __crt_calloc in
rtld-malloc.c. When out of memory __crt_calloc calls morecore, which always
adds NPOOLPAGES (128K) to the requested size (circa 128 bytes for a mutex).
This way pthread_mutex_init and others will eventually fail when the address
space is both limited and fragmented.
A simple fix will be to retry morepages(amt/pagesz) every time
morepages(amt/pagesz + NPOOLPAGES) fails.

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