dmaengine: at_xdmac: Fix locking in tasklet

Tasklets run with all the interrupts enabled. This means that we should
replace all the (already present) spin_lock_irqsave() uses in the tasklet
with spin_lock_irq() to protect being interrupted by a IRQ which tries
to get the same lock (via calls to device_prep_dma_* for example).

spin_lock and spin_lock_bh in tasklets are not enough to protect from IRQs,
update these to spin_lock_irq().

at_xdmac_advance_work() can be called with all the interrupts enabled (when
called from tasklet), or with interrupts disabled (when called from
at_xdmac_issue_pending). Move the locking in the callers to be able to use
spin_lock_irq() and spin_lock_irqsave() for these cases.

Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Acked-by: Ludovic Desroches <ludovic.desroches@microchip.com>
Link: https://lore.kernel.org/r/20200123140237.125799-10-tudor.ambarus@microchip.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>

diff --git a/drivers/dma/at_xdmac.c b/drivers/dma/at_xdmac.c
index 31321da69ae68fbe15285e9c7e9bddce6a8fd5e9..bb0eaf38b59450af447927773de71afa4f518b01 100644 (file)
--- a/drivers/dma/at_xdmac.c
+++ b/drivers/dma/at_xdmac.c
@@ -1543,9 +1543,6 @@ 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_irqsave(&atchan->lock, flags);
 
        /*
         * If channel is enabled, do nothing, advance_work will be triggered
@@ -1559,8 +1556,6 @@ static void at_xdmac_advance_work(struct at_xdmac_chan *atchan)
                if (!desc->active_xfer)
                        at_xdmac_start_xfer(atchan, desc);
        }
-
-       spin_unlock_irqrestore(&atchan->lock, flags);
 }
 
 static void at_xdmac_handle_cyclic(struct at_xdmac_chan *atchan)
@@ -1596,7 +1591,7 @@ static void at_xdmac_handle_error(struct at_xdmac_chan *atchan)
        if (atchan->irq_status & AT_XDMAC_CIS_ROIS)
                dev_err(chan2dev(&atchan->chan), "request overflow error!!!");
 
-       spin_lock_bh(&atchan->lock);
+       spin_lock_irq(&atchan->lock);
 
        /* Channel must be disabled first as it's not done automatically */
        at_xdmac_write(atxdmac, AT_XDMAC_GD, atchan->mask);
@@ -1607,7 +1602,7 @@ static void at_xdmac_handle_error(struct at_xdmac_chan *atchan)
                                    struct at_xdmac_desc,
                                    xfer_node);
 
-       spin_unlock_bh(&atchan->lock);
+       spin_unlock_irq(&atchan->lock);
 
        /* Print bad descriptor's details if needed */
        dev_dbg(chan2dev(&atchan->chan),
@@ -1640,21 +1635,21 @@ static void at_xdmac_tasklet(unsigned long data)
                if (atchan->irq_status & error_mask)
                        at_xdmac_handle_error(atchan);
 
-               spin_lock(&atchan->lock);
+               spin_lock_irq(&atchan->lock);
                desc = list_first_entry(&atchan->xfers_list,
                                        struct at_xdmac_desc,
                                        xfer_node);
                dev_vdbg(chan2dev(&atchan->chan), "%s: desc 0x%p\n", __func__, desc);
                if (!desc->active_xfer) {
                        dev_err(chan2dev(&atchan->chan), "Xfer not active: exiting");
-                       spin_unlock(&atchan->lock);
+                       spin_unlock_irq(&atchan->lock);
                        return;
                }
 
                txd = &desc->tx_dma_desc;
 
                at_xdmac_remove_xfer(atchan, desc);
-               spin_unlock(&atchan->lock);
+               spin_unlock_irq(&atchan->lock);
 
                dma_cookie_complete(txd);
                if (txd->flags & DMA_PREP_INTERRUPT)
@@ -1662,7 +1657,9 @@ static void at_xdmac_tasklet(unsigned long data)
 
                dma_run_dependencies(txd);
 
+               spin_lock_irq(&atchan->lock);
                at_xdmac_advance_work(atchan);
+               spin_unlock_irq(&atchan->lock);
        }
 }
 
@@ -1723,11 +1720,15 @@ static irqreturn_t at_xdmac_interrupt(int irq, void *dev_id)
 static void at_xdmac_issue_pending(struct dma_chan *chan)
 {
        struct at_xdmac_chan *atchan = to_at_xdmac_chan(chan);
+       unsigned long flags;
 
        dev_dbg(chan2dev(&atchan->chan), "%s\n", __func__);
 
-       if (!at_xdmac_chan_is_cyclic(atchan))
+       if (!at_xdmac_chan_is_cyclic(atchan)) {
+               spin_lock_irqsave(&atchan->lock, flags);
                at_xdmac_advance_work(atchan);
+               spin_unlock_irqrestore(&atchan->lock, flags);
+       }
 
        return;
 }