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    Subject[RFC][PATCH] Use proper casting with signed timespec.tv_nsec values
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    All,
    I recently ran into a bug with an older kernel where xtime's tv_nsec
    field had accumulated more then 2 seconds worth of time. The timespec's
    tv_nsec is a signed long, however gettimeofday() treats it as an
    unsigned long. Thus when the failure occured, very strange and difficult
    to debug time problems occurred.

    The main cause of the problem I was seeing is already fixed in mainline,
    however just to be safe, I figured the following patch would be wise.

    I only audited i386 and x86_64, however other arches probably could have
    similar signed problems as well.

    Please let me know if you have any further comments or feedback.

    thanks
    -john

    linux-2.6.13_signed-tv_nsec_A0.patch
    ====================================
    diff --git a/arch/i386/kernel/time.c b/arch/i386/kernel/time.c
    --- a/arch/i386/kernel/time.c
    +++ b/arch/i386/kernel/time.c
    @@ -156,7 +156,7 @@ void do_gettimeofday(struct timeval *tv)
    usec += lost * (USEC_PER_SEC / HZ);

    sec = xtime.tv_sec;
    - usec += (xtime.tv_nsec / 1000);
    + usec += (unsigned long)xtime.tv_nsec / 1000;
    } while (read_seqretry(&xtime_lock, seq));

    while (usec >= 1000000) {
    diff --git a/arch/x86_64/kernel/time.c b/arch/x86_64/kernel/time.c
    --- a/arch/x86_64/kernel/time.c
    +++ b/arch/x86_64/kernel/time.c
    @@ -128,7 +128,7 @@ void do_gettimeofday(struct timeval *tv)
    seq = read_seqbegin(&xtime_lock);

    sec = xtime.tv_sec;
    - usec = xtime.tv_nsec / 1000;
    + usec = (unsigned long)xtime.tv_nsec / 1000;

    /* i386 does some correction here to keep the clock
    monotonous even when ntpd is fixing drift.
    diff --git a/kernel/timer.c b/kernel/timer.c
    --- a/kernel/timer.c
    +++ b/kernel/timer.c
    @@ -824,7 +824,7 @@ static void update_wall_time(unsigned lo
    do {
    ticks--;
    update_wall_time_one_tick();
    - if (xtime.tv_nsec >= 1000000000) {
    + if ((unsigned long)xtime.tv_nsec >= 1000000000) {
    xtime.tv_nsec -= 1000000000;
    xtime.tv_sec++;
    second_overflow();

    -
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