Re: [PATCH 2.6.12.5 1/2] lib: allow idr to be used in irq context

[James Bottomley]

On Sun, 2005-08-21 at 20:52 -0700, Andrew Morton wrote:
> erp.  posix_timers has its own irq-safe lock, so we're doing extra,
> unneeded locking in that code path.

Possibly, the posix timer code is rather convoluted in this area so I'm
not entirely sure my analysis is correct.

> I think providing locking inside idr.c was always a mistake - generally we
> rely on caller-provided locking for such things.

Well, the reason is because they wanted lockless pre-alloc.  If you do
it locked, you can't use GFP_KERNEL for the memory allocation flag which
rather defeats its purpose.

Perhaps the bug is in the API.  We have pre-allocate, new, find and
remove.  Perhaps what we're missing is a reuse all of which could then
rely on caller provided locking, with pre-alloc and remove requiring
user context but new, find and reuse being happy in irq context.

James


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