linux-kernel - [PATCH 4.9 42/93] dmaengine: iota: ioat_alloc_chan_resources should not perform sleeping allocations.

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Message-Id: <20170320174737.494758136@linuxfoundation.org>
Date:   Mon, 20 Mar 2017 18:51:17 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Krister Johansen <kjlx@...pleofstupid.com>,
        Dave Jiang <dave.jiang@...el.com>,
        Vinod Koul <vinod.koul@...el.com>
Subject: [PATCH 4.9 42/93] dmaengine: iota: ioat_alloc_chan_resources should not perform sleeping allocations.

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Krister Johansen <kjlx@...pleofstupid.com>

commit 21d25f6a4217e755906cb548b55ddab39d0e88b9 upstream.

On a kernel with DEBUG_LOCKS, ioat_free_chan_resources triggers an
in_interrupt() warning.  With PROVE_LOCKING, it reports detecting a
SOFTIRQ-safe to SOFTIRQ-unsafe lock ordering in the same code path.

This is because dma_generic_alloc_coherent() checks if the GFP flags
permit blocking.  It allocates from different subsystems if blocking is
permitted.  The free path knows how to return the memory to the correct
allocator.  If GFP_KERNEL is specified then the alloc and free end up
going through cma_alloc(), which uses mutexes.

Given that ioat_free_chan_resources() can be called in interrupt
context, ioat_alloc_chan_resources() must specify GFP_NOWAIT so that the
allocations do not block and instead use an allocator that uses
spinlocks.

Signed-off-by: Krister Johansen <kjlx@...pleofstupid.com>
Acked-by: Dave Jiang <dave.jiang@...el.com>
Signed-off-by: Vinod Koul <vinod.koul@...el.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/dma/ioat/init.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/drivers/dma/ioat/init.c
+++ b/drivers/dma/ioat/init.c
@@ -691,7 +691,7 @@ static int ioat_alloc_chan_resources(str
 	/* doing 2 32bit writes to mmio since 1 64b write doesn't work */
 	ioat_chan->completion =
 		dma_pool_zalloc(ioat_chan->ioat_dma->completion_pool,
-				GFP_KERNEL, &ioat_chan->completion_dma);
+				GFP_NOWAIT, &ioat_chan->completion_dma);
 	if (!ioat_chan->completion)
 		return -ENOMEM;

@@ -701,7 +701,7 @@ static int ioat_alloc_chan_resources(str
 	       ioat_chan->reg_base + IOAT_CHANCMP_OFFSET_HIGH);

 	order = IOAT_MAX_ORDER;
-	ring = ioat_alloc_ring(c, order, GFP_KERNEL);
+	ring = ioat_alloc_ring(c, order, GFP_NOWAIT);
 	if (!ring)
 		return -ENOMEM;