[patch, -rc5-mm2] lock validator: drivers/block/floppy.c fixes
From: Ingo Molnar
Date: Sat Jun 03 2006 - 10:29:31 EST
Subject: lock validator: drivers/block/floppy.c fixes
From: Ingo Molnar <mingo@xxxxxxx>
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@xxxxxxx>
---
drivers/block/floppy.c | 61 +------------------------------------------------
1 file changed, 2 insertions(+), 59 deletions(-)
Index: linux/drivers/block/floppy.c
===================================================================
--- linux.orig/drivers/block/floppy.c
+++ linux/drivers/block/floppy.c
@@ -251,18 +251,6 @@ static int irqdma_allocated;
#include <linux/cdrom.h> /* for the compatibility eject ioctl */
#include <linux/completion.h>
-/*
- * Interrupt freeing also means /proc VFS work - dont do it
- * from interrupt context. We push this work into keventd:
- */
-static void fd_free_irq_fn(void *data)
-{
- fd_free_irq();
-}
-
-static DECLARE_WORK(fd_free_irq_work, fd_free_irq_fn, NULL);
-
-
static struct request *current_req;
static struct request_queue *floppy_queue;
static void do_fd_request(request_queue_t * q);
@@ -573,21 +561,6 @@ static int floppy_grab_irq_and_dma(void)
static void floppy_release_irq_and_dma(void);
/*
- * Interrupt, DMA and region freeing must not be done from IRQ
- * context - e.g. irq-unregistration means /proc VFS work, region
- * release takes an irq-unsafe lock, etc. So we push this work
- * into keventd:
- */
-static void fd_release_fn(void *data)
-{
- mutex_lock(&open_lock);
- floppy_release_irq_and_dma();
- mutex_unlock(&open_lock);
-}
-
-static DECLARE_WORK(floppy_release_irq_and_dma_work, fd_release_fn, NULL);
-
-/*
* The "reset" variable should be tested whenever an interrupt is scheduled,
* after the commands have been sent. This is to ensure that the driver doesn't
* get wedged when the interrupt doesn't come because of a failed command.
@@ -843,15 +816,6 @@ static int set_dor(int fdc, char mask, c
UDRS->select_date = jiffies;
}
}
- /*
- * We should propagate failures to grab the resources back
- * nicely from here. Actually we ought to rewrite the fd
- * driver some day too.
- */
- if (newdor & FLOPPY_MOTOR_MASK)
- floppy_grab_irq_and_dma();
- if (olddor & FLOPPY_MOTOR_MASK)
- schedule_work(&floppy_release_irq_and_dma_work);
return olddor;
}
@@ -909,8 +873,6 @@ static int _lock_fdc(int drive, int inte
line);
return -1;
}
- if (floppy_grab_irq_and_dma() == -1)
- return -EBUSY;
if (test_and_set_bit(0, &fdc_busy)) {
DECLARE_WAITQUEUE(wait, current);
@@ -967,7 +929,6 @@ static inline void unlock_fdc(void)
if (elv_next_request(floppy_queue))
do_fd_request(floppy_queue);
spin_unlock_irqrestore(&floppy_lock, flags);
- schedule_work(&floppy_release_irq_and_dma_work);
wake_up(&fdc_wait);
}
@@ -3714,8 +3675,8 @@ static int floppy_release(struct inode *
}
if (!UDRS->fd_ref)
opened_bdev[drive] = NULL;
- floppy_release_irq_and_dma();
mutex_unlock(&open_lock);
+
return 0;
}
@@ -3746,9 +3707,6 @@ static int floppy_open(struct inode *ino
if (UDRS->fd_ref == -1 || (UDRS->fd_ref && (filp->f_flags & O_EXCL)))
goto out2;
- if (floppy_grab_irq_and_dma())
- goto out2;
-
if (filp->f_flags & O_EXCL)
UDRS->fd_ref = -1;
else
@@ -3825,7 +3783,6 @@ out:
UDRS->fd_ref--;
if (!UDRS->fd_ref)
opened_bdev[drive] = NULL;
- floppy_release_irq_and_dma();
out2:
mutex_unlock(&open_lock);
return res;
@@ -3842,14 +3799,9 @@ static int check_floppy_change(struct ge
return 1;
if (time_after(jiffies, UDRS->last_checked + UDP->checkfreq)) {
- if (floppy_grab_irq_and_dma()) {
- return 1;
- }
-
lock_fdc(drive, 0);
poll_drive(0, 0);
process_fd_request();
- floppy_release_irq_and_dma();
}
if (UTESTF(FD_DISK_CHANGED) ||
@@ -4399,7 +4351,6 @@ static int __init floppy_init(void)
fdc = 0;
del_timer(&fd_timeout);
current_drive = 0;
- floppy_release_irq_and_dma();
initialising = 0;
if (have_no_fdc) {
DPRINT("no floppy controllers found\n");
@@ -4559,7 +4510,7 @@ static void floppy_release_irq_and_dma(v
if (irqdma_allocated) {
fd_disable_dma();
fd_free_dma();
- schedule_work(&fd_free_irq_work);
+ fd_free_irq();
irqdma_allocated = 0;
}
set_dor(0, ~0, 8);
@@ -4664,20 +4615,12 @@ void cleanup_module(void)
del_timer_sync(&fd_timer);
blk_cleanup_queue(floppy_queue);
- /*
- * Wait for any asynchronous floppy_release_irq_and_dma()
- * calls to finish first:
- */
- flush_scheduled_work();
-
if (usage_count)
floppy_release_irq_and_dma();
/* eject disk, if any */
fd_eject(0);
- flush_scheduled_work(); /* fd_free_irq() might be pending */
-
wait_for_completion(&device_release);
}
-
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