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Dimitri Sivanich 71416bea5a [IA64] disable irq's and check need_resched before safe_halt

While sending interrupts to a cpu to repeatedly wake a thread, on occasion
that thread will take a full timer tick cycle (4002 usec in my case)
to wakeup.

The problem concerns a race condition in the code around the safe_halt()
call in the default_idle() routine.  Setting 'nohalt' on the kernel
command line causes the long wakeups to disappear.

void
default_idle (void)
{
        local_irq_enable();
        while (!need_resched()) {
-->             if (can_do_pal_halt)
-->                     safe_halt();
                else

A timer tick could arrive between the check for !need_resched and the
actual call to safe_halt() (which does a pal call to PAL_HALT_LIGHT).
By the time the timer tick completes, a thread that might now need to run
could get held up for as long as a timer tick waiting for the halted cpu.

I'm proposing that we disable irq's and check need_resched again before
calling safe_halt().  Does anyone see any problem with this approach?

Signed-off-by: Dimitri Sivanich <sivanich@sgi.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>

2007-08-13 10:17:23 -07:00

configs

Pull ia64-clocksource into release branch

2007-07-20 11:26:47 -07:00

dig

[PATCH] tty: Remove include of screen_info.h from tty.h

2006-07-10 13:24:16 -07:00

Merge master.kernel.org:/pub/scm/linux/kernel/git/jejb/scsi-rc-fixes-2.6

2007-07-29 17:22:03 -07:00

ia32

[IA64] Remove a few duplicate includes

2007-07-30 16:28:59 -07:00