lkml.org 
[lkml]   [2001]   [May]   [11]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] __up_read and gcc-3.0
Petr Vandrovec wrote:
>
> Hi Alan,
> can you apply this patch to next 2.4.4-acX ? This fixes problem with
> gcc3.0 (20010426) unable to compile this under some conditions. As
> __up_write() uses same code ("i".... instead of tmp variable), I think
> that you should apply this. It can cause slower code, as gcc cannot
> move "movl -RWSEM_ACTIVE_READ_BIAS,%edx" away from "xadd" anymore,
> but as "lock xadd" is slow anyway, it should not matter.
>
> I looked at generated code in cases where it originally failed, and
> generated code looks OK to me.
> Thanks,
> Petr Vandrovec
> vandrove@vc.cvut.cz
>
> diff -urdN linux/include/asm-i386/rwsem.h linux/include/asm-i386/rwsem.h
> --- linux/include/asm-i386/rwsem.h Fri Apr 27 22:48:24 2001
> +++ linux/include/asm-i386/rwsem.h Wed May 9 16:31:57 2001
> @@ -148,9 +148,9 @@
> */
> static inline void __up_read(struct rw_semaphore *sem)
> {
> - __s32 tmp = -RWSEM_ACTIVE_READ_BIAS;
> __asm__ __volatile__(
> "# beginning __up_read\n\t"
> + " movl %2,%%edx\n\t"
> LOCK_PREFIX " xadd %%edx,(%%eax)\n\t" /* subtracts 1, returns the old value */
> " js 2f\n\t" /* jump if the lock is being waited upon */
> "1:\n\t"
> @@ -164,9 +164,9 @@
> " jmp 1b\n"
> ".previous\n"
> "# ending __up_read\n"
> - : "+m"(sem->count), "+d"(tmp)
> - : "a"(sem)
> - : "memory", "cc");
> + : "+m"(sem->count)
> + : "a"(sem), "i"(-RWSEM_ACTIVE_READ_BIAS)
> + : "memory", "cc", "edx");
> }
>
> /*

Hi Petr,

My solution to this was to relax +d(tmp) to +m(tmp). Posted a few days ago.
I have larger problems with 2.4.5-pre1 and have not gone back to check what
comes out. Being a product of pure reason (and not much of that), mine
deserves suspicion.

Cheers,
Tom

--
The Daemons lurk and are dumb. -- Emerson
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-03-22 12:52    [W:0.042 / U:2.028 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site