Hello, On 05/20/2010 01:33 PM, Prashant wrote: > I have a question related to code which is almost same in the > current kernel. I don't know whether this is the right mailing list > for the following question. linux-scsi would probably fit better (cc'd). > When a sata drive is unplugged, its corresponding sdev's state is set > to SDEV_OFFLINE. Now if IO requests are still comming on the same device, > They will be killed by calling scsi_kill_request(). > > 1) scsi_kill_request does following things: > i) Unlock request queue > ii) Increment host_busy count > iii) Lock request queue > iv) Calls __scsi_done() > > 2) __scsi_done() does following things: > i) set request completion data > ii) Calls blk_completion_request() > > 3) blk_completion_request() does following things: > i) Adds request->donelist to blk_cpu_done softirq queue > and raise the softirq (which is scsi_softirq_done) > > 4) next sequence is: > scsi_softirq_done >> scsi_finish_command >> scsi_device_unbusy() > > 5) scsi_device_unbusy() again locks the request_queue. This is the place where > we can get into the spinlock recursion. > > Is this correct? Please correct me if something is wrong. Raising softirq defers the work to another context and grabbing the same lock from softirq handler doesn't constitute a recursive locking. Please try to reproduce the problem on recent kernel w/ lockdep enabled. Thanks. -- tejun -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
