Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752824Ab0LTBVF (ORCPT ); Sun, 19 Dec 2010 20:21:05 -0500 Received: from mail.linux-iscsi.org ([67.23.28.174]:34448 "EHLO linux-iscsi.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752232Ab0LTBVA (ORCPT ); Sun, 19 Dec 2010 20:21:00 -0500 Subject: Re: [PATCH 01/12] libiscsi: Convert to host_lock less w/ interrupts disabled internally From: "Nicholas A. Bellinger" To: Matthew Wilcox Cc: linux-scsi , linux-kernel , James Bottomley , Jeff Garzik , Christoph Hellwig , FUJITA Tomonori , Hannes Reinecke , Mike Christie In-Reply-To: <20101219233835.GJ1263@parisc-linux.org> References: <1292793727-31957-1-git-send-email-nab@linux-iscsi.org> <1292793727-31957-2-git-send-email-nab@linux-iscsi.org> <20101219233835.GJ1263@parisc-linux.org> Content-Type: text/plain Date: Sun, 19 Dec 2010 17:15:03 -0800 Message-Id: <1292807703.20840.29.camel@haakon2.linux-iscsi.org> Mime-Version: 1.0 X-Mailer: Evolution 2.22.3.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4091 Lines: 118 On Sun, 2010-12-19 at 16:38 -0700, Matthew Wilcox wrote: > On Sun, Dec 19, 2010 at 01:21:56PM -0800, Nicholas A. Bellinger wrote: > > This patch changes iscsi_queuecommand_lck() to a host_lock less > > iscsi_queuecommand() that will internally disable interrupts using > > session->lock and drop the now legacy host_lock unlock. > > I think this patch is buggy. Before, iscsi_queuecommand_lck is called with > interrupts disabled. Now, it's called with interrupts disabled. Elsewhere, > session->lock is acquired with bh's disabled: > > void iscsi_put_task(struct iscsi_task *task) > { > struct iscsi_session *session = task->conn->session; > > spin_lock_bh(&session->lock); > > So I think you need to convert the > spin_lock(&session->lock); > in iscsi_queuecommand_lck to at least a spin_lock_bh, and possibly > a spin_lock_irq -- it's not clear to me whether it needs to exclude > against interrupt context, or only BH context. In some places, it's > taken with spin_lock_irqsave(). > > I'd play it safe and use _irq, but someone more confident with this code > might choose to only use _bh. > Hmmm, indeed.. I must have dropped this recently as the last patch for libiscsi posted below still has been converted to spin_lock_irq() for session->lock here: http://marc.info/?l=linux-scsi&m=128952081412461&w=2 Converting back to spin_lock_irq() usage for the moment.. Thanks alot of noticing this.. MikeC and Hannes, do you think this is safe to use spin_lock_bh() as well..? --nab > > Signed-off-by: Nicholas A. Bellinger > > --- > > drivers/scsi/libiscsi.c | 10 ++-------- > > 1 files changed, 2 insertions(+), 8 deletions(-) > > > > diff --git a/drivers/scsi/libiscsi.c b/drivers/scsi/libiscsi.c > > index c15fde8..5535782 100644 > > --- a/drivers/scsi/libiscsi.c > > +++ b/drivers/scsi/libiscsi.c > > @@ -1599,7 +1599,7 @@ enum { > > FAILURE_SESSION_NOT_READY, > > }; > > > > -static int iscsi_queuecommand_lck(struct scsi_cmnd *sc, void (*done)(struct scsi_cmnd *)) > > +int iscsi_queuecommand(struct Scsi_Host *sh, struct scsi_cmnd *sc) > > { > > struct iscsi_cls_session *cls_session; > > struct Scsi_Host *host; > > @@ -1609,13 +1609,11 @@ static int iscsi_queuecommand_lck(struct scsi_cmnd *sc, void (*done)(struct scsi > > struct iscsi_conn *conn; > > struct iscsi_task *task = NULL; > > > > - sc->scsi_done = done; > > sc->result = 0; > > sc->SCp.ptr = NULL; > > > > host = sc->device->host; > > ihost = shost_priv(host); > > - spin_unlock(host->host_lock); > > > > cls_session = starget_to_session(scsi_target(sc->device)); > > session = cls_session->dd_data; > > @@ -1706,7 +1704,6 @@ static int iscsi_queuecommand_lck(struct scsi_cmnd *sc, void (*done)(struct scsi > > > > session->queued_cmdsn++; > > spin_unlock(&session->lock); > > - spin_lock(host->host_lock); > > return 0; > > > > prepd_reject: > > @@ -1716,7 +1713,6 @@ reject: > > spin_unlock(&session->lock); > > ISCSI_DBG_SESSION(session, "cmd 0x%x rejected (%d)\n", > > sc->cmnd[0], reason); > > - spin_lock(host->host_lock); > > return SCSI_MLQUEUE_TARGET_BUSY; > > > > prepd_fault: > > @@ -1732,12 +1728,10 @@ fault: > > scsi_out(sc)->resid = scsi_out(sc)->length; > > scsi_in(sc)->resid = scsi_in(sc)->length; > > } > > - done(sc); > > - spin_lock(host->host_lock); > > + sc->scsi_done(sc); > > return 0; > > } > > > > -DEF_SCSI_QCMD(iscsi_queuecommand) > > EXPORT_SYMBOL_GPL(iscsi_queuecommand); > > > > int iscsi_change_queue_depth(struct scsi_device *sdev, int depth, int reason) > > -- > > 1.7.3.4 > > > > -- > > To unsubscribe from this list: send the line "unsubscribe linux-scsi" in > > the body of a message to majordomo@vger.kernel.org > > More majordomo info at http://vger.kernel.org/majordomo-info.html > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/