On 9/6/06, Bahadir Balban <bahadir.balban@xxxxxxxxx> wrote:
In linux device drivers 3, block drivers chapter, for block device io
tranfers, a function is defined:
int sbull_transfer_bio(struct sbull_dev *dev, struct bio *bio)
{
...
bio_for_each_segment(bvec, bio, i) {
...
__bio_kmap_atomic(...);
sbull_transfer(...);
__bio_kunmap_atomic(...);
...
}
}
Here, the transfer is not done in process context, and
sbull_transfer() cannot sleep. How could I implement a sleeping
transfer?
The request function of block devices are called in process context
and they can sleep (but end_io is called in interrupt context).
Although in above example sbull_transfer is done in atomic context and
only doing memory transfer not the real IO operation. So you can do
sleep before or after transfering the data or simple use kmap and then
can go into sleep during transfer.
char drivers can sleep and receive data fetched in an irq context, can
I not do this for block drivers?
Sorry I won't able to understand your question, but I can say that you
can sleep in process context whether its char or block driver but if
you got/receive data in irq context either in block or char driver you
can sleep in that context rather can insert the data in a queue and
just return from irq context; later use queued data in process
context.
I hope this helps.
--
Fawad Lateef
--
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