lkml.org 
[lkml]   [2000]   [Sep]   [7]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: spin_lock forgets to clobber memory and other smp fixes [was Re: [patch] waitqueue optimization, 2.4.0-test7]
    Andrea Arcangeli wrote:
    > >int *p;
    > >int func()
    > >{
    > > int x;
    > > x = *p;
    > > __asm__ __volatile__ ("" : : : "memory");
    > > x = *p;
    > > return x;
    > >}
    >
    > Defintely none difference here (-fstrict-aliasing doesn't change anything
    > either).
    >
    > andrea@inspiron:~ > gcc -v
    > Reading specs from /usr/lib/gcc-lib/i486-suse-linux/2.95.2/specs
    > gcc version 2.95.2 19991024 (release)

    I tried it with two compilers, one older than yours and one newer:

    .ident "GCC: (GNU) egcs-2.91.66 19990314/Linux (egcs-1.1.2 release)"
    .ident "GCC: (GNU) 2.96 20000724 (experimental)"

    The command lines were:

    gcc -S -O2 test4.c
    kgcc -S -O2 test4.c

    In both cases, the memory read occurs before "zzz".

    -- Jamie
    -
    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to majordomo@vger.kernel.org
    Please read the FAQ at http://www.tux.org/lkml/

    \
     
     \ /
      Last update: 2005-03-22 12:38    [W:0.022 / U:1.484 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site