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Subjectproblem in md?
Hi Ingo,
IIRC I suspected a possible problem in md_thread() a few weeks ago, and
I proved wrong. But now I'm sure that there could be a problem!

md_thread calls

cli()
for(;;) {
interruptible_sleep_on()
cli();
do_something().
}
are you aware that do_something() is called WITHOUT the global interrupt
lock held?

Let me explain it:
* the initial cli() disables the local interrupts, and acquires the
global lock.
* interruptible_sleep_on() calls spin_lock_irqsave(), and this saves the
_local_ interrupt flag on the stack.
* schedule() releases the global interrupt lock.
* schedule() eventually returns, and interruptible_sleep_on() restores
the _local_ interrupt flag. (hidden in wq_write_unlock_irqrestore().)
* __global_cli() notices that the local interrupts are disabled, and
downgrades the global lock to a local lock.

I think you should add an sti() just before the cli(). You cannot call
the sti() before interruptible_sleep_on(), this could cause a race.

Please correct me if I'm wrong,

Manfred

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