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Message-ID: <BCB48C05FCE8BC4D9E61E841ECBE6DB70D1D9D@039-SN2MPN1-011.039d.mgd.msft.net>
Date: Thu, 2 Aug 2012 04:56:48 +0000
From: Liu Qiang-B32616 <B32616@...escale.com>
To: "Ira W. Snyder" <iws@...o.caltech.edu>
CC: "linux-crypto@...r.kernel.org" <linux-crypto@...r.kernel.org>,
"linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"dan.j.williams@...il.com" <dan.j.williams@...il.com>,
Vinod Koul <vinod.koul@...el.com>,
Tabi Timur-B04825 <B04825@...escale.com>,
"herbert@...dor.apana.org.au" <herbert@...dor.apana.org.au>,
Dan Williams <dan.j.williams@...el.com>,
"davem@...emloft.net" <davem@...emloft.net>
Subject: RE: [PATCH v5 5/6] fsl-dma: use spin_lock_bh to instead of
spin_lock_irqsave
> -----Original Message-----
> From: Ira W. Snyder [mailto:iws@...o.caltech.edu]
> Sent: Thursday, August 02, 2012 1:31 AM
> To: Liu Qiang-B32616
> Cc: linux-crypto@...r.kernel.org; linuxppc-dev@...ts.ozlabs.org; linux-
> kernel@...r.kernel.org; dan.j.williams@...il.com; Vinod Koul; Tabi Timur-
> B04825; herbert@...dor.hengli.com.au; Dan Williams; davem@...emloft.net
> Subject: Re: [PATCH v5 5/6] fsl-dma: use spin_lock_bh to instead of
> spin_lock_irqsave
>
> On Wed, Aug 01, 2012 at 04:50:09PM +0800, qiang.liu@...escale.com wrote:
> > From: Qiang Liu <qiang.liu@...escale.com>
> >
> > - use spin_lock_bh() is the right way to use async_tx api,
> > dma_run_dependencies() should not be protected by spin_lock_irqsave();
> > - use spin_lock_bh to instead of spin_lock_irqsave for improving
> > performance, There is not any place to access descriptor queues in
> > fsl-dma ISR except its tasklet, spin_lock_bh() is more proper here.
> > Interrupts will be turned off and context will be save in irqsave,
> there is needless to use irqsave..
> >
>
> This description is not very clear English. I understand it is not your
> native language. Let me try to help.
>
> """
> The use of spin_lock_irqsave() is a stronger locking mechanism than is
> required throughout the driver. The minimum locking required should be
> used instead.
>
> Change all instances of spin_lock_irqsave() to spin_lock_bh(). All
> manipulation of protected fields is done using tasklet context or weaker,
> which makes spin_lock_bh() the correct choice.
> """
I will modify the description in v6, please check later.
>
> Other than that,
> Acked-by: Ira W. Snyder <iws@...o.caltech.edu>
Thanks.
>
> > Cc: Dan Williams <dan.j.williams@...el.com>
> > Cc: Vinod Koul <vinod.koul@...el.com>
> > Cc: Li Yang <leoli@...escale.com>
> > Cc: Timur Tabi <timur@...escale.com>
> > Signed-off-by: Qiang Liu <qiang.liu@...escale.com>
> > ---
> > drivers/dma/fsldma.c | 30 ++++++++++++------------------
> > 1 files changed, 12 insertions(+), 18 deletions(-)
> >
> > diff --git a/drivers/dma/fsldma.c b/drivers/dma/fsldma.c index
> > bb883c0..e3814aa 100644
> > --- a/drivers/dma/fsldma.c
> > +++ b/drivers/dma/fsldma.c
> > @@ -645,10 +645,9 @@ static dma_cookie_t fsl_dma_tx_submit(struct
> dma_async_tx_descriptor *tx)
> > struct fsldma_chan *chan = to_fsl_chan(tx->chan);
> > struct fsl_desc_sw *desc = tx_to_fsl_desc(tx);
> > struct fsl_desc_sw *child;
> > - unsigned long flags;
> > dma_cookie_t cookie;
> >
> > - spin_lock_irqsave(&chan->desc_lock, flags);
> > + spin_lock_bh(&chan->desc_lock);
> >
> > /*
> > * assign cookies to all of the software descriptors @@ -661,7
> > +660,7 @@ static dma_cookie_t fsl_dma_tx_submit(struct
> dma_async_tx_descriptor *tx)
> > /* put this transaction onto the tail of the pending queue */
> > append_ld_queue(chan, desc);
> >
> > - spin_unlock_irqrestore(&chan->desc_lock, flags);
> > + spin_unlock_bh(&chan->desc_lock);
> >
> > return cookie;
> > }
> > @@ -770,15 +769,14 @@ static void fsldma_free_desc_list_reverse(struct
> > fsldma_chan *chan, static void fsl_dma_free_chan_resources(struct
> > dma_chan *dchan) {
> > struct fsldma_chan *chan = to_fsl_chan(dchan);
> > - unsigned long flags;
> >
> > chan_dbg(chan, "free all channel resources\n");
> > - spin_lock_irqsave(&chan->desc_lock, flags);
> > + spin_lock_bh(&chan->desc_lock);
> > fsldma_cleanup_descriptor(chan);
> > fsldma_free_desc_list(chan, &chan->ld_pending);
> > fsldma_free_desc_list(chan, &chan->ld_running);
> > fsldma_free_desc_list(chan, &chan->ld_completed);
> > - spin_unlock_irqrestore(&chan->desc_lock, flags);
> > + spin_unlock_bh(&chan->desc_lock);
> >
> > dma_pool_destroy(chan->desc_pool);
> > chan->desc_pool = NULL;
> > @@ -997,7 +995,6 @@ static int fsl_dma_device_control(struct dma_chan
> > *dchan, {
> > struct dma_slave_config *config;
> > struct fsldma_chan *chan;
> > - unsigned long flags;
> > int size;
> >
> > if (!dchan)
> > @@ -1007,7 +1004,7 @@ static int fsl_dma_device_control(struct
> > dma_chan *dchan,
> >
> > switch (cmd) {
> > case DMA_TERMINATE_ALL:
> > - spin_lock_irqsave(&chan->desc_lock, flags);
> > + spin_lock_bh(&chan->desc_lock);
> >
> > /* Halt the DMA engine */
> > dma_halt(chan);
> > @@ -1017,7 +1014,7 @@ static int fsl_dma_device_control(struct dma_chan
> *dchan,
> > fsldma_free_desc_list(chan, &chan->ld_running);
> > chan->idle = true;
> >
> > - spin_unlock_irqrestore(&chan->desc_lock, flags);
> > + spin_unlock_bh(&chan->desc_lock);
> > return 0;
> >
> > case DMA_SLAVE_CONFIG:
> > @@ -1059,11 +1056,10 @@ static int fsl_dma_device_control(struct
> > dma_chan *dchan, static void fsl_dma_memcpy_issue_pending(struct
> > dma_chan *dchan) {
> > struct fsldma_chan *chan = to_fsl_chan(dchan);
> > - unsigned long flags;
> >
> > - spin_lock_irqsave(&chan->desc_lock, flags);
> > + spin_lock_bh(&chan->desc_lock);
> > fsl_chan_xfer_ld_queue(chan);
> > - spin_unlock_irqrestore(&chan->desc_lock, flags);
> > + spin_unlock_bh(&chan->desc_lock);
> > }
> >
> > /**
> > @@ -1076,15 +1072,14 @@ static enum dma_status fsl_tx_status(struct
> > dma_chan *dchan, {
> > struct fsldma_chan *chan = to_fsl_chan(dchan);
> > enum dma_status ret;
> > - unsigned long flags;
> >
> > ret = dma_cookie_status(dchan, cookie, txstate);
> > if (ret == DMA_SUCCESS)
> > return ret;
> >
> > - spin_lock_irqsave(&chan->desc_lock, flags);
> > + spin_lock_bh(&chan->desc_lock);
> > fsldma_cleanup_descriptor(chan);
> > - spin_unlock_irqrestore(&chan->desc_lock, flags);
> > + spin_unlock_bh(&chan->desc_lock);
> >
> > return dma_cookie_status(dchan, cookie, txstate); } @@ -1163,11
> > +1158,10 @@ static irqreturn_t fsldma_chan_irq(int irq, void *data)
> > static void dma_do_tasklet(unsigned long data) {
> > struct fsldma_chan *chan = (struct fsldma_chan *)data;
> > - unsigned long flags;
> >
> > chan_dbg(chan, "tasklet entry\n");
> >
> > - spin_lock_irqsave(&chan->desc_lock, flags);
> > + spin_lock_bh(&chan->desc_lock);
> >
> > /* the hardware is now idle and ready for more */
> > chan->idle = true;
> > @@ -1175,7 +1169,7 @@ static void dma_do_tasklet(unsigned long data)
> > /* Run all cleanup for this descriptor */
> > fsldma_cleanup_descriptor(chan);
> >
> > - spin_unlock_irqrestore(&chan->desc_lock, flags);
> > + spin_unlock_bh(&chan->desc_lock);
> >
> > chan_dbg(chan, "tasklet exit\n");
> > }
> > --
> > 1.7.5.1
> >
> >
> > _______________________________________________
> > Linuxppc-dev mailing list
> > Linuxppc-dev@...ts.ozlabs.org
> > https://lists.ozlabs.org/listinfo/linuxppc-dev
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