This is the mail archive of the glibc-bugs@sourceware.org mailing list for the glibc project.


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]
Other format: [Raw text]

[Bug nptl/15640] The ARM port of lll_unlock uses atomic compare and swap to release a lock


http://sourceware.org/bugzilla/show_bug.cgi?id=15640

--- Comment #7 from Dinar Temirbulatov <dtemirbulatov at gmail dot com> ---
(In reply to Abhishek Deb from comment #6)
> Since the preprocessor macro atomic_exchange_rel was not explicity defined,
> it gets defined to atomic_compare_and_exhange_*, which is defined using
> gcc's atomic built-in __sync_val_compare_and_swap.
> 
> But I think atomic exchange is not the same as atomic compare and exchange.
> An atomic exchange should be defined as ldex, stex, bne, whereas atomic
> compare and exchange is defined as ldex, cmp, bne, stex, bne. 
> 
> Doesn't look like gcc's atomic builtin in provides an explicit function to
> do that http://gcc.gnu.org/onlinedocs/gcc-4.6.2/gcc/Atomic-Builtins.html.
> 
> However, gcc's atomic built in provides __sync_fetch_and_* . Can it be used
> to build an atomic exchange.

yes, All correct, except I think that it needs cmp after stex.

-- 
You are receiving this mail because:
You are on the CC list for the bug.


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]