Messages in this thread | | | Subject | Re: [PATCH 01/12] libiscsi: Convert to host_lock less w/ interrupts disabled internally | From | "Nicholas A. Bellinger" <> | Date | Mon, 20 Dec 2010 01:30:13 -0800 |
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On Sun, 2010-12-19 at 19:07 -0700, Matthew Wilcox wrote: > On Sun, Dec 19, 2010 at 05:22:06PM -0800, Nicholas A. Bellinger wrote: > > Actually sorry, Mike Christie did already make a clarification on this > > subject here: > > > > http://marc.info/?l=linux-scsi&m=129010439421506&w=2 > > > > I had originally thought the same that session->lock should be using > > some flavour of spin_lock_irq*() as well, but apparently this is not the > > case for libiscsi. > > Right, so it seems. "the session lock is just locked in softirqs/timers" > means that it does need to be the _bh() version of spin_lock though. > > I'm actually not sure ... is it safe to use the _bh versions in BH > context? I think it is because the preempt count is nested, unlike the > _irq variants of spinlocks. >
Hmmm, fair point. Merging the following incremental patch to convert session->lock to use spin_lock_bh() in iscsi_queuecommand() into lock_less-LLDs-for-38-v3:
commit 744f1c119b3fb0c1a6b3c67a7b490e234d1a7e75 Author: Nicholas Bellinger <nab@linux-iscsi.org> Date: Mon Dec 20 09:17:19 2010 +0000
libiscsi: Convert iscsi_queuecommand to use spin_lock_bh This patch converts iscsi_queuecommand() code to obtain struct iscsi_session->lock using spin_lock_bh() to properly handle bottom-half context operation. Reported-by: Matthew Wilcox <willy@linux.intel.com> Signed-off-by: Nicholas A. Bellinger <nab@linux-iscsi.org>
After a quick audit of iscsi_session->lock usage, and I see that iscsi_complete_pdu(), iscsi_tmf_timedout(), iscsi_eh_cmd_timed_out(), iscsi_check_transport_timeouts() are using spin_lock(), and iscsi_session_failure() and iscsi_conn_failure() are using spin_lock_irqsave().
Mike and Hannes, would you guys mind commenting on this..? From what I can determine these should all be converted to use spin_lock_bh(), yes..?
--nab
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