On 11/06/2015 01:52 PM, Michael Christie wrote:

On Nov 5, 2015, at 6:56 PM, Chris Leech <cle...@redhat.com> wrote:

On Thu, Nov 05, 2015 at 02:33:44PM -0200, Guilherme G. Piccoli wrote:

Interesting. From the trace, the list debugging code is detecting
corruption when removing a task from some list.  Could be the connection
mgmtqueue, cmdqueue, or requeue.

After the locking change adding a task to any of those lists is under
the session fwrd_lock, but the call to iscsi_complete_task which deletes
the task from whatever list it's on is under the back_lock.

Am I missing something, or is splitting a linked list across two locks a
major failing of this change?

You are right. Patch is really wrong. Not sure what I was thinking when I 
merged it. It has had multiple issues now,

Or and Shlomo, I am going to just revert the patch for now until I can do some 
performance testing with a patch to add back correct locking and also 
re-rerview the patch. Maybe instead of locks I can just use some kfifos too.

Thanks very much Chris and Michael.

Chris: good point. As far as I understand, back_lock can be taken from inside fwd_lock, so if all those back_locks are taken inside fwd_locks, shouldn't be an issue. I'll investigate a little more, it's an interesting patch and issue.

Since Michael plans to revert the commit on mainline, I'd ask you, if you can, to add me on future discussions regarding this patch.

Thanks for your help,


Guilherme

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