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Message-ID: <55700020.5070307@atmel.com>
Date: Thu, 4 Jun 2015 09:37:04 +0200
From: Nicolas Ferre <nicolas.ferre@...el.com>
To: Ludovic Desroches <ludovic.desroches@...el.com>,
<linux-arm-kernel@...ts.infradead.org>,
<dmaengine@...r.kernel.org>, <linux-kernel@...r.kernel.org>
CC: <vinod.koul@...el.com>, <maxime.ripard@...e-electrons.com>
Subject: Re: [PATCH 1/2] dmaengine: at_xdmac: lock fixes
Le 03/06/2015 16:52, Ludovic Desroches a écrit :
> Using _bh variant for spin locks causes this kind of warning:
> Starting logging: ------------[ cut here ]------------
> WARNING: CPU: 0 PID: 3 at /ssd_drive/linux/kernel/softirq.c:151
> __local_bh_enable_ip+0xe8/0xf4()
> Modules linked in:
> CPU: 0 PID: 3 Comm: ksoftirqd/0 Not tainted 4.1.0-rc2+ #94
> Hardware name: Atmel SAMA5
> [<c0013c04>] (unwind_backtrace) from [<c00118a4>] (show_stack+0x10/0x14)
> [<c00118a4>] (show_stack) from [<c001bbcc>]
> (warn_slowpath_common+0x80/0xac)
> [<c001bbcc>] (warn_slowpath_common) from [<c001bc14>]
> (warn_slowpath_null+0x1c/0x24)
> [<c001bc14>] (warn_slowpath_null) from [<c001e28c>]
> (__local_bh_enable_ip+0xe8/0xf4)
> [<c001e28c>] (__local_bh_enable_ip) from [<c01fdbd0>]
> (at_xdmac_device_terminate_all+0xf4/0x100)
> [<c01fdbd0>] (at_xdmac_device_terminate_all) from [<c02221a4>]
> (atmel_complete_tx_dma+0x34/0xf4)
> [<c02221a4>] (atmel_complete_tx_dma) from [<c01fe4ac>]
> (at_xdmac_tasklet+0x14c/0x1ac)
> [<c01fe4ac>] (at_xdmac_tasklet) from [<c001de58>]
> (tasklet_action+0x68/0xb4)
> [<c001de58>] (tasklet_action) from [<c001dfdc>]
> (__do_softirq+0xfc/0x238)
> [<c001dfdc>] (__do_softirq) from [<c001e140>] (run_ksoftirqd+0x28/0x34)
> [<c001e140>] (run_ksoftirqd) from [<c0033a3c>]
> (smpboot_thread_fn+0x138/0x18c)
> [<c0033a3c>] (smpboot_thread_fn) from [<c0030e7c>] (kthread+0xdc/0xf0)
> [<c0030e7c>] (kthread) from [<c000f480>] (ret_from_fork+0x14/0x34)
> ---[ end trace b57b14a99c1d8812 ]---
>
> It comes from the fact that devices can called some code from the DMA
Isn't there a typo in the previous line?
> controller with irq disabled. _bh variant is not intended to be used in
> this case since it can enable irqs. Switch to irqsave/irqrestore variant to
> avoid this situation.
>
> Signed-off-by: Ludovic Desroches <ludovic.desroches@...el.com>
> Cc: stable@...r.kernel.org # 4.0 and later
Yes:
Acked-by: Nicolas Ferre <nicolas.ferre@...el.com>
> ---
> drivers/dma/at_xdmac.c | 85 ++++++++++++++++++++++++++++----------------------
> 1 file changed, 48 insertions(+), 37 deletions(-)
>
> diff --git a/drivers/dma/at_xdmac.c b/drivers/dma/at_xdmac.c
> index 9b602a6..4a7e9c6 100644
> --- a/drivers/dma/at_xdmac.c
> +++ b/drivers/dma/at_xdmac.c
> @@ -421,8 +421,9 @@ static dma_cookie_t at_xdmac_tx_submit(struct dma_async_tx_descriptor *tx)
> struct at_xdmac_desc *desc = txd_to_at_desc(tx);
> struct at_xdmac_chan *atchan = to_at_xdmac_chan(tx->chan);
> dma_cookie_t cookie;
> + unsigned long irqflags;
>
> - spin_lock_bh(&atchan->lock);
> + spin_lock_irqsave(&atchan->lock, irqflags);
> cookie = dma_cookie_assign(tx);
>
> dev_vdbg(chan2dev(tx->chan), "%s: atchan 0x%p, add desc 0x%p to xfers_list\n",
> @@ -431,7 +432,7 @@ static dma_cookie_t at_xdmac_tx_submit(struct dma_async_tx_descriptor *tx)
> if (list_is_singular(&atchan->xfers_list))
> at_xdmac_start_xfer(atchan, desc);
>
> - spin_unlock_bh(&atchan->lock);
> + spin_unlock_irqrestore(&atchan->lock, irqflags);
> return cookie;
> }
>
> @@ -591,11 +592,13 @@ at_xdmac_prep_slave_sg(struct dma_chan *chan, struct scatterlist *sgl,
> unsigned int sg_len, enum dma_transfer_direction direction,
> unsigned long flags, void *context)
> {
> - struct at_xdmac_chan *atchan = to_at_xdmac_chan(chan);
> - struct at_xdmac_desc *first = NULL, *prev = NULL;
> - struct scatterlist *sg;
> - int i;
> - unsigned int xfer_size = 0;
> + struct at_xdmac_chan *atchan = to_at_xdmac_chan(chan);
> + struct at_xdmac_desc *first = NULL, *prev = NULL;
> + struct scatterlist *sg;
> + int i;
> + unsigned int xfer_size = 0;
> + unsigned long irqflags;
> + struct dma_async_tx_descriptor *ret = NULL;
>
> if (!sgl)
> return NULL;
> @@ -611,7 +614,7 @@ at_xdmac_prep_slave_sg(struct dma_chan *chan, struct scatterlist *sgl,
> flags);
>
> /* Protect dma_sconfig field that can be modified by set_slave_conf. */
> - spin_lock_bh(&atchan->lock);
> + spin_lock_irqsave(&atchan->lock, irqflags);
>
> /* Prepare descriptors. */
> for_each_sg(sgl, sg, sg_len, i) {
> @@ -622,8 +625,7 @@ at_xdmac_prep_slave_sg(struct dma_chan *chan, struct scatterlist *sgl,
> mem = sg_dma_address(sg);
> if (unlikely(!len)) {
> dev_err(chan2dev(chan), "sg data length is zero\n");
> - spin_unlock_bh(&atchan->lock);
> - return NULL;
> + goto spin_unlock;
> }
> dev_dbg(chan2dev(chan), "%s: * sg%d len=%u, mem=0x%08x\n",
> __func__, i, len, mem);
> @@ -633,8 +635,7 @@ at_xdmac_prep_slave_sg(struct dma_chan *chan, struct scatterlist *sgl,
> dev_err(chan2dev(chan), "can't get descriptor\n");
> if (first)
> list_splice_init(&first->descs_list, &atchan->free_descs_list);
> - spin_unlock_bh(&atchan->lock);
> - return NULL;
> + goto spin_unlock;
> }
>
> /* Linked list descriptor setup. */
> @@ -673,13 +674,15 @@ at_xdmac_prep_slave_sg(struct dma_chan *chan, struct scatterlist *sgl,
> xfer_size += len;
> }
>
> - spin_unlock_bh(&atchan->lock);
>
> first->tx_dma_desc.flags = flags;
> first->xfer_size = xfer_size;
> first->direction = direction;
> + ret = &first->tx_dma_desc;
>
> - return &first->tx_dma_desc;
> +spin_unlock:
> + spin_unlock_irqrestore(&atchan->lock, irqflags);
> + return ret;
> }
>
> static struct dma_async_tx_descriptor *
> @@ -692,6 +695,7 @@ at_xdmac_prep_dma_cyclic(struct dma_chan *chan, dma_addr_t buf_addr,
> struct at_xdmac_desc *first = NULL, *prev = NULL;
> unsigned int periods = buf_len / period_len;
> int i;
> + unsigned long irqflags;
>
> dev_dbg(chan2dev(chan), "%s: buf_addr=%pad, buf_len=%zd, period_len=%zd, dir=%s, flags=0x%lx\n",
> __func__, &buf_addr, buf_len, period_len,
> @@ -710,16 +714,16 @@ at_xdmac_prep_dma_cyclic(struct dma_chan *chan, dma_addr_t buf_addr,
> for (i = 0; i < periods; i++) {
> struct at_xdmac_desc *desc = NULL;
>
> - spin_lock_bh(&atchan->lock);
> + spin_lock_irqsave(&atchan->lock, irqflags);
> desc = at_xdmac_get_desc(atchan);
> if (!desc) {
> dev_err(chan2dev(chan), "can't get descriptor\n");
> if (first)
> list_splice_init(&first->descs_list, &atchan->free_descs_list);
> - spin_unlock_bh(&atchan->lock);
> + spin_unlock_irqrestore(&atchan->lock, irqflags);
> return NULL;
> }
> - spin_unlock_bh(&atchan->lock);
> + spin_unlock_irqrestore(&atchan->lock, irqflags);
> dev_dbg(chan2dev(chan),
> "%s: desc=0x%p, tx_dma_desc.phys=%pad\n",
> __func__, desc, &desc->tx_dma_desc.phys);
> @@ -1036,6 +1040,7 @@ at_xdmac_prep_dma_memcpy(struct dma_chan *chan, dma_addr_t dest, dma_addr_t src,
> | AT_XDMAC_CC_SIF(0)
> | AT_XDMAC_CC_MBSIZE_SIXTEEN
> | AT_XDMAC_CC_TYPE_MEM_TRAN;
> + unsigned long irqflags;
>
> dev_dbg(chan2dev(chan), "%s: src=%pad, dest=%pad, len=%zd, flags=0x%lx\n",
> __func__, &src, &dest, len, flags);
> @@ -1051,9 +1056,9 @@ at_xdmac_prep_dma_memcpy(struct dma_chan *chan, dma_addr_t dest, dma_addr_t src,
>
> dev_dbg(chan2dev(chan), "%s: remaining_size=%zu\n", __func__, remaining_size);
>
> - spin_lock_bh(&atchan->lock);
> + spin_lock_irqsave(&atchan->lock, irqflags);
> desc = at_xdmac_get_desc(atchan);
> - spin_unlock_bh(&atchan->lock);
> + spin_unlock_irqrestore(&atchan->lock, irqflags);
> if (!desc) {
> dev_err(chan2dev(chan), "can't get descriptor\n");
> if (first)
> @@ -1123,6 +1128,7 @@ at_xdmac_tx_status(struct dma_chan *chan, dma_cookie_t cookie,
> int residue;
> u32 cur_nda, mask, value;
> u8 dwidth = 0;
> + unsigned long flags;
>
> ret = dma_cookie_status(chan, cookie, txstate);
> if (ret == DMA_COMPLETE)
> @@ -1131,7 +1137,7 @@ at_xdmac_tx_status(struct dma_chan *chan, dma_cookie_t cookie,
> if (!txstate)
> return ret;
>
> - spin_lock_bh(&atchan->lock);
> + spin_lock_irqsave(&atchan->lock, flags);
>
> desc = list_first_entry(&atchan->xfers_list, struct at_xdmac_desc, xfer_node);
>
> @@ -1141,8 +1147,7 @@ at_xdmac_tx_status(struct dma_chan *chan, dma_cookie_t cookie,
> */
> if (!desc->active_xfer) {
> dma_set_residue(txstate, desc->xfer_size);
> - spin_unlock_bh(&atchan->lock);
> - return ret;
> + goto spin_unlock;
> }
>
> residue = desc->xfer_size;
> @@ -1173,14 +1178,14 @@ at_xdmac_tx_status(struct dma_chan *chan, dma_cookie_t cookie,
> }
> residue += at_xdmac_chan_read(atchan, AT_XDMAC_CUBC) << dwidth;
>
> - spin_unlock_bh(&atchan->lock);
> -
> dma_set_residue(txstate, residue);
>
> dev_dbg(chan2dev(chan),
> "%s: desc=0x%p, tx_dma_desc.phys=%pad, tx_status=%d, cookie=%d, residue=%d\n",
> __func__, desc, &desc->tx_dma_desc.phys, ret, cookie, residue);
>
> +spin_unlock:
> + spin_unlock_irqrestore(&atchan->lock, flags);
> return ret;
> }
>
> @@ -1201,8 +1206,9 @@ static void at_xdmac_remove_xfer(struct at_xdmac_chan *atchan,
> static void at_xdmac_advance_work(struct at_xdmac_chan *atchan)
> {
> struct at_xdmac_desc *desc;
> + unsigned long flags;
>
> - spin_lock_bh(&atchan->lock);
> + spin_lock_irqsave(&atchan->lock, flags);
>
> /*
> * If channel is enabled, do nothing, advance_work will be triggered
> @@ -1217,7 +1223,7 @@ static void at_xdmac_advance_work(struct at_xdmac_chan *atchan)
> at_xdmac_start_xfer(atchan, desc);
> }
>
> - spin_unlock_bh(&atchan->lock);
> + spin_unlock_irqrestore(&atchan->lock, flags);
> }
>
> static void at_xdmac_handle_cyclic(struct at_xdmac_chan *atchan)
> @@ -1353,12 +1359,13 @@ static int at_xdmac_device_config(struct dma_chan *chan,
> {
> struct at_xdmac_chan *atchan = to_at_xdmac_chan(chan);
> int ret;
> + unsigned long flags;
>
> dev_dbg(chan2dev(chan), "%s\n", __func__);
>
> - spin_lock_bh(&atchan->lock);
> + spin_lock_irqsave(&atchan->lock, flags);
> ret = at_xdmac_set_slave_config(chan, config);
> - spin_unlock_bh(&atchan->lock);
> + spin_unlock_irqrestore(&atchan->lock, flags);
>
> return ret;
> }
> @@ -1367,18 +1374,19 @@ static int at_xdmac_device_pause(struct dma_chan *chan)
> {
> struct at_xdmac_chan *atchan = to_at_xdmac_chan(chan);
> struct at_xdmac *atxdmac = to_at_xdmac(atchan->chan.device);
> + unsigned long flags;
>
> dev_dbg(chan2dev(chan), "%s\n", __func__);
>
> if (test_and_set_bit(AT_XDMAC_CHAN_IS_PAUSED, &atchan->status))
> return 0;
>
> - spin_lock_bh(&atchan->lock);
> + spin_lock_irqsave(&atchan->lock, flags);
> at_xdmac_write(atxdmac, AT_XDMAC_GRWS, atchan->mask);
> while (at_xdmac_chan_read(atchan, AT_XDMAC_CC)
> & (AT_XDMAC_CC_WRIP | AT_XDMAC_CC_RDIP))
> cpu_relax();
> - spin_unlock_bh(&atchan->lock);
> + spin_unlock_irqrestore(&atchan->lock, flags);
>
> return 0;
> }
> @@ -1387,18 +1395,19 @@ static int at_xdmac_device_resume(struct dma_chan *chan)
> {
> struct at_xdmac_chan *atchan = to_at_xdmac_chan(chan);
> struct at_xdmac *atxdmac = to_at_xdmac(atchan->chan.device);
> + unsigned long flags;
>
> dev_dbg(chan2dev(chan), "%s\n", __func__);
>
> - spin_lock_bh(&atchan->lock);
> + spin_lock_irqsave(&atchan->lock, flags);
> if (!at_xdmac_chan_is_paused(atchan)) {
> - spin_unlock_bh(&atchan->lock);
> + spin_unlock_irqrestore(&atchan->lock, flags);
> return 0;
> }
>
> at_xdmac_write(atxdmac, AT_XDMAC_GRWR, atchan->mask);
> clear_bit(AT_XDMAC_CHAN_IS_PAUSED, &atchan->status);
> - spin_unlock_bh(&atchan->lock);
> + spin_unlock_irqrestore(&atchan->lock, flags);
>
> return 0;
> }
> @@ -1408,10 +1417,11 @@ static int at_xdmac_device_terminate_all(struct dma_chan *chan)
> struct at_xdmac_desc *desc, *_desc;
> struct at_xdmac_chan *atchan = to_at_xdmac_chan(chan);
> struct at_xdmac *atxdmac = to_at_xdmac(atchan->chan.device);
> + unsigned long flags;
>
> dev_dbg(chan2dev(chan), "%s\n", __func__);
>
> - spin_lock_bh(&atchan->lock);
> + spin_lock_irqsave(&atchan->lock, flags);
> at_xdmac_write(atxdmac, AT_XDMAC_GD, atchan->mask);
> while (at_xdmac_read(atxdmac, AT_XDMAC_GS) & atchan->mask)
> cpu_relax();
> @@ -1421,7 +1431,7 @@ static int at_xdmac_device_terminate_all(struct dma_chan *chan)
> at_xdmac_remove_xfer(atchan, desc);
>
> clear_bit(AT_XDMAC_CHAN_IS_CYCLIC, &atchan->status);
> - spin_unlock_bh(&atchan->lock);
> + spin_unlock_irqrestore(&atchan->lock, flags);
>
> return 0;
> }
> @@ -1431,8 +1441,9 @@ static int at_xdmac_alloc_chan_resources(struct dma_chan *chan)
> struct at_xdmac_chan *atchan = to_at_xdmac_chan(chan);
> struct at_xdmac_desc *desc;
> int i;
> + unsigned long flags;
>
> - spin_lock_bh(&atchan->lock);
> + spin_lock_irqsave(&atchan->lock, flags);
>
> if (at_xdmac_chan_is_enabled(atchan)) {
> dev_err(chan2dev(chan),
> @@ -1463,7 +1474,7 @@ static int at_xdmac_alloc_chan_resources(struct dma_chan *chan)
> dev_dbg(chan2dev(chan), "%s: allocated %d descriptors\n", __func__, i);
>
> spin_unlock:
> - spin_unlock_bh(&atchan->lock);
> + spin_unlock_irqrestore(&atchan->lock, flags);
> return i;
> }
>
>
--
Nicolas Ferre
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