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Groups > linux.kernel > #1383733
| From | Borislav Petkov <bp@alien8.de> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: [PATCH 10/11] x86, rwsem: provide __down_write_killable |
| Date | 2016-04-20 22:50 +0200 |
| Message-ID | <rq7eq-5Ab-9@gated-at.bofh.it> (permalink) |
| References | (4 earlier) <rnphw-7zX-21@gated-at.bofh.it> <rnqdA-8e7-25@gated-at.bofh.it> <rnsyK-1lV-15@gated-at.bofh.it> <rq0FY-fr-19@gated-at.bofh.it> <rq4JC-3Ai-49@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
On Wed, Apr 20, 2016 at 11:04:05AM -0700, H. Peter Anvin wrote:
> The reason it breaks is because the same register can't be an
> input-output register and a separate input. However, the input side of
> the input-output is probably undefined, and so gcc may not notice.
So Michal and I talked about this a while ago. Why do we need the '"a"
(sem)' input dependency if '"+a" (ret)' already supplies the same thing?
There's also that "=d" (tmp) thing which we don't really need as an
output, right?
I.e., can we simplify like this?
---
#define ____down_write(sem, slow_path) \
({ \
long tmp = RWSEM_ACTIVE_WRITE_BIAS; \
struct rw_semaphore* ret = sem; \
\
asm volatile("# beginning down_write\n\t" \
LOCK_PREFIX " xadd %[tmp],(%[ret])\n\t" \
/* adds 0xffff0001, returns the old value */ \
" test " __ASM_SEL(%w[tmp],%k[tmp]) "," __ASM_SEL(%w[tmp],%k[tmp]) "\n\t" \
/* was the active mask 0 before? */\
" jz 1f\n" \
" call " slow_path "\n" \
"1:\n" \
"# ending down_write" \
: "+m" (sem->count), [ret] "+a" (ret) \
: [tmp] "d" (tmp) \
: "memory", "cc"); \
ret; \
})
--
Regards/Gruss,
Boris.
ECO tip #101: Trim your mails when you reply.
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Re: [PATCH 10/11] x86, rwsem: provide __down_write_killable Peter Zijlstra <peterz@infradead.org> - 2016-04-20 15:50 +0200
Re: [PATCH 10/11] x86, rwsem: provide __down_write_killable "H. Peter Anvin" <hpa@zytor.com> - 2016-04-20 20:10 +0200
Re: [PATCH 10/11] x86, rwsem: provide __down_write_killable Borislav Petkov <bp@alien8.de> - 2016-04-20 22:50 +0200
Re: [PATCH 10/11] x86, rwsem: provide __down_write_killable Michal Hocko <mhocko@kernel.org> - 2016-04-20 23:00 +0200
Re: [PATCH 10/11] x86, rwsem: provide __down_write_killable "H. Peter Anvin" <hpa@zytor.com> - 2016-04-20 23:10 +0200
Re: [PATCH 10/11] x86, rwsem: provide __down_write_killable Borislav Petkov <bp@alien8.de> - 2016-04-20 23:40 +0200
Re: [PATCH 10/11] x86, rwsem: provide __down_write_killable "H. Peter Anvin" <hpa@zytor.com> - 2016-04-21 00:40 +0200
Re: [PATCH 10/11] x86, rwsem: provide __down_write_killable Borislav Petkov <bp@alien8.de> - 2016-04-21 13:40 +0200
Re: [PATCH 10/11] x86, rwsem: provide __down_write_killable Michal Hocko <mhocko@kernel.org> - 2016-04-21 15:10 +0200
Re: [PATCH 10/11] x86, rwsem: provide __down_write_killable Borislav Petkov <bp@alien8.de> - 2016-04-21 15:30 +0200
[PATCH] x86/locking/rwsem: Cleanup ____down_write() Borislav Petkov <bp@alien8.de> - 2016-04-27 14:10 +0200
[tip:locking/rwsem] locking/rwsem, x86: Clean up ____down_write() tip-bot for Borislav Petkov <tipbot@zytor.com> - 2016-04-28 12:30 +0200
Re: [PATCH 10/11] x86, rwsem: provide __down_write_killable Ingo Molnar <mingo@kernel.org> - 2016-04-22 09:00 +0200
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