On 06/25/13 15:45, James Bottomley wrote:
On Tue, 2013-06-25 at 11:01 +0200, Bart Van Assche wrote:
There is a difference though between moving the EH kthread_stop() call
and the patch at the start of this thread: moving the EH kthread_stop()
call does not prevent that an ioctl like SG_SCSI_RESET triggers an eh_*
callback after scsi_remove_host() has finished. However, the
scsi_begin_eh() / scsi_end_eh() functions do prevent that an ioctl can
cause an eh_* callback to be invoked after scsi_remove_device() finished.
OK, but this doesn't tell me what you're trying to achieve.
An eh function is allowable as long as the host hadn't had the release
callback executed. That means you must have to have a reference to the
device/host to execute the eh function, which is currently guaranteed
for all invocations.
That raises a new question: how is an LLD expected to clean up resources
without triggering a race condition ? What you wrote means that it's not
safe for an LLD to start cleaning up the resources needed by the eh_*
callbacks immediately after scsi_remove_device() returns since it it not
guaranteed that at that time all references to the device have already
been dropped.
Bart.
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