From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dan Carpenter Subject: Re: [PATCH 2/3] scsi: arcmsr: Fix suspend/resume of ACB_ADAPTER_TYPE_B part 2 Date: Tue, 22 Jan 2019 10:48:16 +0300 Message-ID: <20190122074816.GC11828@kadam> References: <1547696703.4339.21.camel@Centos6.3-64> <20190117070227.GM4504@kadam> <1547714827.5079.19.camel@Centos6.3-64> <20190117091646.GA11828@kadam> <1547718748.5079.34.camel@Centos6.3-64> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <1547718748.5079.34.camel@Centos6.3-64> Sender: linux-kernel-owner@vger.kernel.org To: Ching Huang Cc: martin.petersen@oracle.com, James.Bottomley@HansenPartnership.com, linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org, hch@infradead.org, colin.king@canonical.com List-Id: linux-scsi@vger.kernel.org On Thu, Jan 17, 2019 at 05:52:28PM +0800, Ching Huang wrote: > On Thu, 2019-01-17 at 12:16 +0300, Dan Carpenter wrote: > > On Thu, Jan 17, 2019 at 04:47:07PM +0800, Ching Huang wrote: > > > On Thu, 2019-01-17 at 10:59 +0300, Dan Carpenter wrote: > > > > On Thu, Jan 17, 2019 at 11:45:03AM +0800, Ching Huang wrote: > > > > > >From Ching Huang > > > > > > > > > > Fix suspend/resume of ACB_ADAPTER_TYPE_B part 2. > > > > > > > > > > > > > What does this look like from a user perspective? Does it fail every > > > > time or does it only fail sometimes? > > > > > > > > What's the bug exactly? > > > > > > > > There is no Fixes tag... > > > >From user's perspective, hibernate/resume are OK. > > > But following IO may cause 'isr get an illegal ccb command' in > > > log/messages sometime. > > > > > > > > > > You will need to resend with that information included in the commit > > message. > OK. I will resend this patch later. > > > > > > > Signed-off-by: Ching Huang > > > > > --- > > > > > > > > > > diff --git a/drivers/scsi/arcmsr/arcmsr.h b/drivers/scsi/arcmsr/arcmsr.h > > > > > index a94c513..b98c632 100755 > > > > > --- a/drivers/scsi/arcmsr/arcmsr.h > > > > > +++ b/drivers/scsi/arcmsr/arcmsr.h > > > > > @@ -508,9 +508,9 @@ struct MessageUnit_A > > > > > struct MessageUnit_B > > > > > { > > > > > uint32_t post_qbuffer[ARCMSR_MAX_HBB_POSTQUEUE]; > > > > > - uint32_t done_qbuffer[ARCMSR_MAX_HBB_POSTQUEUE]; > > > > > + volatile uint32_t done_qbuffer[ARCMSR_MAX_HBB_POSTQUEUE]; > > > > > > > > There is a well known rule of thumb that when someone uses "volatile" > > > > in the kernel it means there is a locking problem... Is this __iomem or > > > > something? > > > The done_qbuffer was a command completion queue, it was an area written > > > by IO processor and read by device driver. So, ... > > > > I'm not totally positive I understand this sentence. I can find a bunch > > of places which read from this buffer, but I haven't immediately found > > which place writes to it. Can you give me a function name that I should > > read? > Well, we allocate memory for struct MessageUnit_B in > arcmsr_alloc_ccb_pool(), by assign to acb->dma_coherent_handle2. > Then we tell IO controller its DMA address in arcmsr_iop_confirm(). > When a command was completed, controller's firmware program will write a > completion ccb in done_qbuffer through DMA. So, you can't see any driver > funtion write to it. DMA memory doesn't need to be marked as volatile. regards, dan carpenter