From: Szabolcs Nagy <szabolcs.nagy@arm.com>
To: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Cc: libc-alpha@sourceware.org, Florian Weimer <fweimer@redhat.com>,
Aurelien Jarno <aurelien@aurel32.net>
Subject: Re: [PATCH v2] nptl: Handle spurious EINTR when thread cancellation is disabled (BZ#29029)
Date: Tue, 19 Apr 2022 10:44:17 +0000 [thread overview]
Message-ID: <Yl6SgX023L24o27O@arm.com> (raw)
In-Reply-To: <20220414154947.2187880-1-adhemerval.zanella@linaro.org>
The 04/14/2022 12:49, Adhemerval Zanella via Libc-alpha 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
>
> Reviewed-by: Florian Weimer <fweimer@redhat.com>
> Tested-by: Aurelien Jarno <aurelien@aurel32.net>
> ---
> v2: Fixed some typos and extended pthread_cancel comments.
since this commit various cancel tests fail for me (unreliably)
on aarch64 e.g. failures from 2 different test runs:
FAIL: nptl/tst-cancel17
FAIL: nptl/tst-cancelx5
FAIL: nptl/tst-cond7
FAIL: nptl/tst-pthread-raise-blocked-self
FAIL: nptl/tst-pthread_cancel-select-loop
FAIL: nptl/tst-cancelx20
FAIL: nptl/tst-cond7
FAIL: nptl/tst-cond8
FAIL: nptl/tst-join12
FAIL: nptl/tst-key3
FAIL: nptl/tst-pthread_cancel-select-loop
an example run of nptl/tst-cond7
$ elf/ld.so --library-path . nptl/tst-cond7 --direct
round 0
child created
parent: joining now
round 1
child created
parent: joining now
round 2
child created
parent: joining now
round 3
child created
parent: joining now
round 4
child created
parent: joining now
where it is blocked forever: it seems pthread_cancel returns without
sending a signal (__pthread_kill_internal is not called) so join hangs.
next prev parent reply other threads:[~2022-04-19 10:44 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-14 15:49 Adhemerval Zanella
2022-04-14 18:26 ` Adhemerval Zanella
2022-04-19 10:44 ` Szabolcs Nagy [this message]
2022-04-19 12:18 ` Adhemerval Zanella
2022-04-19 12:23 ` Adhemerval Zanella
2022-04-19 12:10 ` Szabolcs Nagy
2022-04-19 12:30 ` Adhemerval Zanella
2022-04-19 12:46 ` Szabolcs Nagy
2022-04-19 13:12 ` Adhemerval Zanella
2022-07-12 21:27 ` Noah Goldstein
2022-07-12 21:28 ` Noah Goldstein
2022-07-13 12:57 ` Adhemerval Zanella Netto
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