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SubjectRe: floppy driver assumes INITIAL_JIFFIES == 0


On Thu, 3 Jun 2010, Linus Torvalds wrote:
>
> But I don't see why. I'll dig around the timer stuff a bit more. If it
> only happens with that INITIAL_JIFFIES thing, it must be clearly somehow
> related to a timer happening (or not happening) too early.

Hmm. I don't see anything. In most cases, having whatever variable
pointing to jiffies in the future (which 0 would be for the
INITIAL_JIFFIES case) should be fine - at most it would make the timeout
way too long, not break anything. They tend to be bases for timeouts, ie
you have things like

fd_wait_for_completion(DRS->select_date + DP->select_delay, ...

where we set a timeout based on when we did something.

The one case that seems iffy for is "last_checked", which contains when we
last checked the disk change state. It being in the future could cause
problems, since it would make us think that a disk change state is valid
when it really shouldn't be.

Anyway, does this patch make any difference? It just makes floppy
initialization set up some of those fields too.

Untested. I don't have the hardware.

Linus

---
drivers/block/floppy.c | 5 +++++
1 files changed, 5 insertions(+), 0 deletions(-)
diff --git a/drivers/block/floppy.c b/drivers/block/floppy.c
index 90c4038..c7e83de 100644
--- a/drivers/block/floppy.c
+++ b/drivers/block/floppy.c
@@ -4180,6 +4180,8 @@ static int __init floppy_init(void)
return -ENODEV;
#endif

+ set_debugt();
+
raw_cmd = NULL;

for (dr = 0; dr < N_DRIVE; dr++) {
@@ -4267,6 +4269,9 @@ static int __init floppy_init(void)
set_bit(FD_DISK_CHANGED_BIT, &UDRS->flags);
set_bit(FD_VERIFY_BIT, &UDRS->flags);
UDRS->fd_device = -1;
+ UDRS->last_checked = jiffies;
+ UDRS->select_date = jiffies;
+ UDRS->spinup_date = jiffies;
floppy_track_buffer = NULL;
max_buffer_sectors = 0;
}

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