Messages in this thread | | | From | Roger Larsson <> | Subject | Re: Patch: linux-2.5.8-pre1/kernel/exit.c change caused BUG() at boot time | Date | Thu, 4 Apr 2002 23:34:04 +0200 |
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On torsdagen den 4 april 2002 21.26, Robert Love wrote: > On Thu, 2002-04-04 at 14:14, Linus Torvalds wrote: > > The answer is that preempt_schedule() illegally sets > > > > current->state = TASK_RUNNING; > > > > without asking the process whether that's OK. The SMP code never does > > anything like that. > > Well Ingo added that ;) > > We used to just set a flag in the preempt_count that marked the task as > preempted and made sure on its next trip into schedule it ran again. >
How about doing:
asmlinkage void preempt_schedule(void) { unsigned long saved_state;
if (unlikely(preempt_get_count())) return;
preempt_disable(); /* or use an atomic operation */ saved_state = current->state; current->state = TASK_RUNNING; preempt_enable_no_resched(); /* we are scheduling anyway... */ schedule(); current->state = saved_state; }
It is unlikely to get preemption between schedule() and the setting since schedule it self checks - the window is small. And when it hits if will correctly restore the correct value.
Note this code does not need to solve the FLAG problem.
current->state |= FLAG * PREEMPT * current->state |= FLAG schedule() current->state &= ~FLAG schedule() with flag disabled
/RogerL
-- Roger Larsson Skellefteå Sweden
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