Re: [PATCH] 2.2.14 make_request SMP safe?

[Ingo Molnar]

On Thu, 13 Apr 2000, Roger Larsson wrote:

> 	if (buffer_locked(bh))
> 		return;
> 	lock_buffer(bh);
> 
> But since interrupts are not disabled (IMHO) and no other locks are
> held (IMHO) there is a small (and rather unlikely) window for a
> dead-lock...

the above 2.2 code is 100% safe because we never lock buffers outside of
the big kernel lock. This was the reason why RAID0 broke subtly in 2.3,
because in 2.3 ll_rw_block() is done outside of the big kernel lock as
well.

interrupts can only unlock buffers, so there is no race. We only have to
synchronize with 'system call level' [non-irq, non-bh, non-tasklet, etc.]
code.

	Ingo