Re: 2.5 Problem Status Report

Jens Axboe
2002-09-11T10:24:49Z

On Wed, Sep 11 2002, Jens Axboe wrote:
> On Wed, Sep 11 2002, Oleg Drokin wrote:
> > Hello!
> >
> > On Wed, Sep 11, 2002 at 09:38:25AM +0200, Ingo Molnar wrote:
> >
> > > > I have preemption disabled.
> > > nevertheless please print out preempt_count() in sched.c - since the big
> > > IRQ cleanups we use the preemption count even if preemption is disabled.
> > > this way we'll know what kind of problem happened - a stuck softirq count,
> > > a stuck hardirq count or an underflow?
> >
> > You was exactly right. preemption count is -1. I inserted chack in
> > dec_preempt_count() and here is updated correct stacktrace. Seems
> > like ide_unmap_buffer is called with some bogus data or something like
> > that. Also I guess the bug is only visible with debug highmem = ON and
> > highmem enabled.
>
> ok I see the bug. it's due to the imbalanced nature of ide_map_buffer()
> vs ide_unmap_buffer(). i'll cook up a fix right away.

Oleg,

Does this make it work?

--- drivers/ide/ide-disk.c~ 2002-09-11 12:27:47.000000000 +0200
+++ drivers/ide/ide-disk.c 2002-09-11 12:28:17.000000000 +0200
@@ -175,7 +175,7 @@
drive->name, rq->sector, rq->sector+nsect-1,
(unsigned long) rq->buffer+(nsect<<9), rq->nr_sectors-nsect);
#endif
- ide_unmap_buffer(to, &flags);
+ ide_unmap_buffer(rq, to, &flags);
rq->sector += nsect;
rq->errors = 0;
i = (rq->nr_sectors -= nsect);
@@ -226,7 +226,7 @@
unsigned long flags;
char *to = ide_map_buffer(rq, &flags);
taskfile_output_data(drive, to, SECTOR_WORDS);
- ide_unmap_buffer(to, &flags);
+ ide_unmap_buffer(rq, to, &flags);
if (HWGROUP(drive)->handler != NULL)
BUG();
ide_set_handler(drive, &write_intr, WAIT_CMD, NULL);
@@ -302,7 +302,7 @@
* re-entering us on the last transfer.
*/
taskfile_output_data(drive, buffer, nsect<<7);
- ide_unmap_buffer(buffer, &flags);
+ ide_unmap_buffer(rq, buffer, &flags);
} while (mcount);

return 0;
@@ -688,7 +688,7 @@
BUG();
ide_set_handler(drive, &write_intr, WAIT_CMD, NULL);
taskfile_output_data(drive, buffer, SECTOR_WORDS);
- ide_unmap_buffer(buffer, &flags);
+ ide_unmap_buffer(rq, buffer, &flags);
}
return ide_started;
}
--- drivers/ide/ide-taskfile.c~ 2002-09-11 12:27:51.000000000 +0200
+++ drivers/ide/ide-taskfile.c 2002-09-11 12:28:25.000000000 +0200
@@ -60,7 +60,7 @@
#endif

#define task_map_rq(rq, flags) ide_map_buffer((rq), (flags))
-#define task_unmap_rq(rq, buf, flags) ide_unmap_buffer((buf), (flags))
+#define task_unmap_rq(rq, buf, flags) ide_unmap_buffer((rq), (buf), (flags))

inline u32 task_read_24 (ide_drive_t *drive)
{
--- include/linux/ide.h~ 2002-09-11 12:27:14.000000000 +0200
+++ include/linux/ide.h 2002-09-11 12:27:29.000000000 +0200
@@ -597,9 +597,10 @@
return rq->buffer + task_rq_offset(rq);
}

-extern inline void ide_unmap_buffer(char *buffer, unsigned long *flags)
+extern inline void ide_unmap_buffer(struct request *rq, char *buffer, unsigned long *flags)
{
- bio_kunmap_irq(buffer, flags);
+ if (rq->bio)
+ bio_kunmap_irq(buffer, flags);
}

/*

--
Jens Axboe