On Wed, Aug 18, 2010 at 01:01:56PM -0700, Andrew Morton wrote: > The surprise new requirement that touch_nmi_watchdog() be called from > non-preemptible code does seem to make sense IMO. It's hard to see why > anyone would be touching the watchdog unless he's spinning in irqs-off > code. Except, of course, when we have a utility function which can be > called from wither irqs-on or irqs-off: acpi_os_stall(). > > That being said, it's not good to introduce new API requirements by > accident! An audit of all callers should first be performed, at least. > > > The surprise new requirement that touch_softlockup_watchdog() be called > from non-preemptible code doesn't make sense IMO. If I have a piece of > code in the kernel which I expect to sit in TASK_UNINTERRUPTIBLE state > for three minutes waiting for my egg to boil, I should be able to do > that and I should be able to touch the softlockup detector without > needing to go non-preemptible. Wow. So after re-reading what the original touch_*_watchdog code did and what I copied to kernel/watchdog.c, I'm a little embarrassed on how I managed to mangle the internals of both those functions. While the idea is the same, the semantics are clearly different. touch_nmi_watchdog had a for_each_cpu_present loop, which means it didn't have to deal with the preempt issue. touch_softlockup_watchdog used __raw_get_cpu_var to excuse itself from dealing with the preempt issue. I'll put together a patch that brings those functions back in line with what they used to be. Sorry for the trouble. Cheers, Don -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
