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Re: [Patch] ARM define atomic_exchange_acq/atomic_exchange_rel to __atomic_exchange_n
- From: "Joseph S. Myers" <joseph at codesourcery dot com>
- To: Dinar Temirbulatov <dtemirbulatov at gmail dot com>
- Cc: <libc-ports at sourceware dot org>, <adeb at nvidia dot com>
- Date: Mon, 2 Sep 2013 15:08:25 +0000
- Subject: Re: [Patch] ARM define atomic_exchange_acq/atomic_exchange_rel to __atomic_exchange_n
- Authentication-results: sourceware.org; auth=none
- References: <CAMnfPmMADb=ZqSmC4J6=fMpQp56uGG8v9MKRj_Ly94kcXEtNZA at mail dot gmail dot com>
On Mon, 2 Sep 2013, Dinar Temirbulatov wrote:
> Another version of change, I added
> and atomic_compare_and_exchange_bool_acq/atomic_compare_and_exchange_boot_rel
> defenitions and also for gcc-4.7 and higher in the case of unsupported
> atomic compare and swap operation, it uses the kernel helper inlines.
> Tested on arm a9 with no new regressions. Ok to commit?
> Oh, sorry. I missed to attach the change. Here it is.
For subsequent patch revisions, please note there should be an extra space
after "#" for preprocessor directives inside #if conditionals, one per
level of #if nesting (other than toplevel multiple-inclusion guards) -
which means that if conditioning existing code, you need to adjust
directives inside that code.
This patch appears to have too much duplication. For example, you
duplicate the definition of __arm_assisted_compare_and_exchange_val_32_acq
- but that should not need any extra conditionals at all (beyond the
existing #ifndef __arm_assisted_compare_and_exchange_val_32_acq), there's
no reason ever not to define it. Similarly, you duplicate
__arch_compare_and_exchange_val_64_acq, but with proper #if structure
there should only need to be one copy of the version that uses
What I think you should aim for is that each definition, or small group of
definitions, uses conditionals in the form
#if __GNUC_PREREQ (4, 7) && defined __GCC_HAVE_SYNC_COMPARE_AND_SWAP_4
/* Version using __atomic_*. */
#elif defined __GCC_HAVE_SYNC_COMPARE_AND_SWAP_4
/* Version using __sync_*. */
/* Version using __arm_assisted_*. */
with cases omitted if not useful for that particular macro (this may
include some macros not being defined at all in some cases). So don't
insert any global conditionals affecting all the existing definitions at
all - look at each block of conditionals and add a third case as needed,
along with any new macros (again with conditionals in that form) that are
Where you use abort () in some definitions, use __arm_link_error ()
instead, like for the existing definitions.
Joseph S. Myers