[PATCH][2.6.7-rc2] gcc-3.4.0 warning in i386 __down_read_trylock()

From: Mikael Pettersson (mikpe_at_csd.uu.se)
Date: 05/30/04

  • Next message: Christian Kujau: "unable to compile 2.4 with gcc-3.4.0" 
    Date:	Sun, 30 May 2004 12:47:05 +0200 (MEST)
To: torvalds@osdl.org

    The i386 __down_read_trylock() code contains a "+m" asm
    constraint, which triggers warnings from gcc-3.4.0:

      gcc -Wp,-MD,fs/xfs/.xfs_iget.o.d -nostdinc -iwithprefix include -D__KERNEL__ -Iinclude -Wall -Wstrict-prototypes -Wno-trigraphs -fno-strict-aliasing -fno-common -pipe -msoft-float -mpreferred-stack-boundary=2 -fno-unit-at-a-time -march=k8 -Iinclude/asm-i386/mach-default -O2 -fomit-frame-pointer -Wdeclaration-after-statement -Ifs/xfs -Ifs/xfs/linux-2.6 -funsigned-char -DKBUILD_BASENAME=xfs_iget -DKBUILD_MODNAME=xfs -c -o fs/xfs/xfs_iget.o fs/xfs/xfs_iget.c
    include/asm/rwsem.h: In function `xfs_ilock_nowait':
    include/asm/rwsem.h:126: warning: read-write constraint does not allow a register
    include/asm/rwsem.h:126: warning: read-write constraint does not allow a register
    include/asm/rwsem.h:126: warning: read-write constraint does not allow a register
    include/asm/rwsem.h:126: warning: read-write constraint does not allow a register

    Fixed by the patch below.

    /Mikael

    diff -ruN linux-2.6.7-rc2/include/asm-i386/rwsem.h linux-2.6.7-rc2.gcc340-fixes/include/asm-i386/rwsem.h
    --- linux-2.6.7-rc2/include/asm-i386/rwsem.h 2003-03-08 17:22:32.000000000 +0100
    +++ linux-2.6.7-rc2.gcc340-fixes/include/asm-i386/rwsem.h 2004-05-30 11:39:07.000000000 +0200
    @@ -134,8 +134,8 @@
                     " jnz 1b\n\t"
                     "2:\n\t"
                     "# ending __down_read_trylock\n\t"
    - : "+m"(sem->count), "=&a"(result), "=&r"(tmp)
    - : "i"(RWSEM_ACTIVE_READ_BIAS)
    + : "=m"(sem->count), "=&a"(result), "=&r"(tmp)
    + : "i"(RWSEM_ACTIVE_READ_BIAS), "m"(sem->count)
                     : "memory", "cc");
             return result>=0 ? 1 : 0;
     }
    -
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