tree a3f0de1022e4459d0eadb1f8583956ab7067011a
parent 5863aa651bd79a6bb15972894306923db088e71c
author Ingo Molnar <mingo@elte.hu> 1151911463 -0700
committer Linus Torvalds <torvalds@g5.osdl.org> 1151965620 -0700

[PATCH] lockdep: floppy.c irq release fix

The lock validator triggered a number of bugs in the floppy driver, all
related to the floppy driver allocating and freeing irq and dma resources from
interrupt context.  The initial solution was to use schedule_work() to push
this into process context, but this caused further problems: for example the
current floppy driver in -mm2 is totally broken and all floppy commands time
out with an error.  (as reported by Barry K.  Nathan)

This patch tries another solution: simply get rid of all that dynamic IRQ and
DMA allocation/freeing.  I doubt it made much sense back in the heydays of
floppies (if two devices raced for DMA or IRQ resources then we didnt handle
those cases too gracefully anyway), and today it makes near zero sense.

So the new code does the simplest and most straightforward thing: allocate IRQ
and DMA resources at module init time, and free them at module removal time.
Dont try to release while the driver is operational.  This, besides making the
floppy driver functional again has an added bonus, floppy IRQ stats are
finally persistent and visible in /proc/interrupts:

  6: 63 XT-PIC-level floppy

Besides normal floppy IO i have also tested IO error handling, motor-off
timeouts, etc.  - and everything seems to be working fine.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>