• john stultz's avatar
    [PATCH] i386 Time: Avoid PIT SMP lockups · 3f4a0b91
    john stultz authored
    Avoid possible PIT livelock issues seen on SMP systems (and reported by
    Andi), by not allowing it as a clocksource on SMP boxes.
    
    However, since the PIT may no longer be present, we have to properly handle
    the cases where SMP systems have TSC skew and fall back from the TSC.
    Since the PIT isn't there, it would "fall back" to the TSC again.  So this
    changes the jiffies rating to 1, and the TSC-bad rating value to 0.
    
    Thus you will get the following behavior priority on i386 systems:
    
    tsc		[if present & stable]
    hpet		[if present]
    cyclone		[if present]
    acpi_pm		[if present]
    pit		[if UP]
    jiffies
    
    Rather then the current more complicated:
    tsc		[if present & stable]
    hpet		[if present]
    cyclone		[if present]
    acpi_pm		[if present]
    pit		[if cpus < 4]
    tsc		[if present & unstable]
    jiffies
    Signed-off-by: default avatarJohn Stultz <johnstul@us.ibm.com>
    Cc: Andi Kleen <ak@suse.de>
    Cc: Ingo Molnar <mingo@elte.hu>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
    3f4a0b91
tsc.c 10.5 KB