Re: [PATCH] nptl: Handle spurious EINTR when thread cancellation is disabled (BZ#29029)

[Aurelien Jarno <aurelien@aurel32.net>]

On 2022-04-07 10:26, Adhemerval Zanella wrote:
> Some Linux interfaces never restart after being interrupted by a signal
> handler, regardless of the use of SA_RESTART [1].  It means that for
> pthread cancellation, if the target thread disables cancellation with
> pthread_setcancelstate and calls such interfaces (like poll or select),
> it should not see spurious EINTR failures due the internal SIGCANCEL.
> 
> However recent changes made pthread_cancel to always sent the internal
> signal, regardless of the target thread cancellation status or type.
> To fix it, the previous semantic is restored, where the cancel signal
> is only sent if the target thread has cancelation enabled in
> asynchronous mode.
> 
> The cancel state and cancel type is moved back to cancelhandling
> and atomic operation are used to synchronize between threads.  The
> patch essentially revert the following commits:
> 
>   8c1c0aae20 nptl: Move cancel type out of cancelhandling
>   2b51742531 nptl: Move cancel state out of cancelhandling
>   26cfbb7162 nptl: Remove CANCELING_BITMASK
> 
> However I changed the atomic operation to follow the internal C11
> semantic and removed the MACRO usage, it simplifies a bit the
> resulting code (and removes another usage of the old atomic macros).
> 
> Checked on x86_64-linux-gnu, i686-linux-gnu, aarch64-linux-gnu,
> and powerpc64-linux-gnu.
> 
> [1] https://man7.org/linux/man-pages/man7/signal.7.html
> ---
>  manual/process.texi            |   3 +-
>  nptl/allocatestack.c           |   2 -
>  nptl/cancellation.c            |  50 ++++++--
>  nptl/cleanup_defer.c           |  42 ++++++-
>  nptl/descr.h                   |  33 ++++--
>  nptl/libc-cleanup.c            |  39 ++++++-
>  nptl/pthread_cancel.c          | 106 ++++++++++++-----
>  nptl/pthread_join_common.c     |   7 +-
>  nptl/pthread_setcancelstate.c  |  26 ++++-
>  nptl/pthread_setcanceltype.c   |  31 ++++-
>  nptl/pthread_testcancel.c      |   9 +-
>  sysdeps/nptl/dl-tls_init_tp.c  |   3 -
>  sysdeps/pthread/Makefile       |   1 +
>  sysdeps/pthread/tst-cancel29.c | 207 +++++++++++++++++++++++++++++++++
>  14 files changed, 473 insertions(+), 86 deletions(-)
>  create mode 100644 sysdeps/pthread/tst-cancel29.c

Thanks a lot for providing a fix so quickly. I confirm the patch works
as expected.

Tested-by: Aurelien Jarno <aurelien@aurel32.net>

-- 
Aurelien Jarno                          GPG: 4096R/1DDD8C9B
aurelien@aurel32.net                 http://www.aurel32.net