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Re: pthread cancellation points missing for fdatasync and lockf in some cases

On 5/5/07, Mike Frysinger <> wrote:
POSIX requires fdatasync() and lockf() be pthread cancellation endpoints but
it looks like they get missed a little in glibc ...

Is there a reference for this?

fdatasync() is generated for Linux simply via syscalls.list as a pass through
to the kernel... the generic case in misc/fdatasync.c relies on fsync() being
a cancellation endpoint ... so here, just Linux is broken it seems

A patch for this would be to add "C" to the fdatasync signature in syscalls.list. See

as for lockf(), this seems to be [incorrectly] done on purpose ... io/lockf.c
talks about relying on fcntl()'s cancellation endpoint when called with
F_SETLKW as that is the only case that POSIX says fcntl() should be a
cancellation endpoint ... however, POSIX does not grant this limitation to
lockf() ... it should always be a cancellation endpoint regardless of the
arguments it is called with

Use LIBC_CANCEL_ASYNC/LIBC_CANCEL_RESET to fix this. Then write a test to prove it works? :-)

Care to file this in the bugzilla so we don't forget.


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