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Re: [PATCH] misc/tst-clone3: Fix waiting for exited thread.


On 02/12/2019 01:53 PM, Stefan Liebler wrote:
On 02/11/2019 01:11 PM, Adhemerval Zanella wrote:


On 11/02/2019 08:59, Florian Weimer wrote:
* Stefan Liebler:

I've first tried to include atomic.h, but it failed building on
x86_64. Thus I'm using the c11 atomic load in the updated patch.
Okay to commit?


As information, I've observed those gcc errors on x86_64:
In file included from ../sysdeps/unix/sysv/linux/x86_64/sysdep.h:30,
                  from ../sysdeps/x86_64/nptl/tls.h:28,
                  from ../sysdeps/x86/atomic-machine.h:23,
                  from ../include/atomic.h:50,
                  from ../sysdeps/unix/sysv/linux/tst-clone3.c:29:
../sysdeps/unix/sysv/linux/dl-sysdep.h: In function
‘_dl_discover_osversion’:
../sysdeps/unix/sysv/linux/dl-sysdep.h:31:42: error: expected
declaration specifiers before ‘attribute_hidden’
  extern int _dl_discover_osversion (void) attribute_hidden;
                                           ^~~~~~~~~~~~~~~~

That's because the test isn't in tests-internal.

+    while ((__tid = __atomic_load_n (ctid_ptr, __ATOMIC_ACQUIRE)) != 0)    \

Actually, that's not a C11 atomic construct, but I think it's okay to
use that here.  (The C11 stuff lives in <stdatomic.h> and should be
functionally equivalent.)

Sorry, this is a pet peeve of mine.  We have three different atomic
access facilities that people refer to as C11 atomics: Our own
<atomic.h>, the GCC __atomic builtins, and <stdatomic.h>.

I still think this contributes to cognitive load, and we should
eliminate all but one (leaving us with new-style atomics and the old
macros in <atomic.h>).  The GCC __atomic builtins have the best freely
available documentation, so they are a natural candidate IMHO.

It really annoying that C11 standard is not freely available from ISO,
although the working draft is still open [1]. I don't have a strong
opinion, but since there is support in the language itself and they
are fully supported by the compiler I also don't see why not prefer it.

[1] http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1570.pdf

Then I have a further update of the patch which uses stdatomic.h and atomic_load_explicit.


ping
okay to commit?


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