[Bug libc/17168] New: Can GLibc expose futex now?

["sstewartgallus00 at mylangara dot bc.ca" <sourceware-bugzilla at sourceware dot org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=17168

            Bug ID: 17168
           Summary: Can GLibc expose futex now?
           Product: glibc
           Version: unspecified
            Status: NEW
          Severity: enhancement
          Priority: P2
         Component: libc
          Assignee: unassigned at sourceware dot org
          Reporter: sstewartgallus00 at mylangara dot bc.ca
                CC: drepper.fsp at gmail dot com

Most application writers should use standard pthread synchronization
functionality and not use low level functionality instead.  However,
certain performance concerned programmers might want to use futexes
directly.  Unfortunately, as FUTEX_WAIT is a blocking system call this
leaves a critical piece of functionality unimplemented and missing.
In the past, one could have used FUTEX_FD to wait on memory locations
to change asynchronously (although it would have been racy).  However,
FUTEX_FD is not supported anymore on Linux (as it is racy).  Now, the
only choice to use FUTEX_WAIT asynchronously is to use multiple
threads and cancel the thread waiting on the memory location to
change.  Except one can't as futex is not exposed by GLibc and I do
not want to try reimplementing pthread_cancel myself which might be
seriously difficult.  Taking the five seconds to wrap the futex calls
with the syscall function is not a problem but I can't use futex
asynchronously without support from GLibc.

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