From dd59b8537f6cb53ab863fafad86a5828f1e889a2 Mon Sep 17 00:00:00 2001
From: Yuri Tikhonov <yur@emcraft.com>
Date: Mon, 12 Jan 2009 15:17:20 -0700
Subject: dmaengine: fix dependency chaining
In dmaengine we track the dependencies between the descriptors
using the 'next' pointers of the structure. These pointers are
set to NULL as soon as the corresponding descriptor has been
submitted to the channel (in dma_run_dependencies()).
But, the first 'next' in chain is still remaining set, regardless
the fact, that tx->next has been already submitted. This may lead to
multiple submissions of the same descriptor. This patch fixes this.
Actually, some previous implementation of the xxx_run_dependencies()
function already had this fix in place. The fdb..0eaf3 commit, beside the
correct things, broke this.
Cc: <stable@kernel.org>
Signed-off-by: Yuri Tikhonov <yur@emcraft.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
drivers/dma/dmaengine.c | 2 ++
1 file changed, 2 insertions(+)
(limited to 'drivers/dma/dmaengine.c')
diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c
index 403dbe781122..6df144a65fef 100644
--- a/drivers/dma/dmaengine.c
+++ b/drivers/dma/dmaengine.c
@@ -961,6 +961,8 @@ void dma_run_dependencies(struct dma_async_tx_descriptor *tx)
if (!dep)
return;
+ /* we'll submit tx->next now, so clear the link */
+ tx->next = NULL;
chan = dep->chan;
/* keep submitting up until a channel switch is detected
--
cgit
From 83436a0560e9ef8af2f0796264dde4bed1415359 Mon Sep 17 00:00:00 2001
From: Dan Williams <dan.j.williams@intel.com>
Date: Mon, 19 Jan 2009 14:39:10 -0700
Subject: dmaengine: kill some dubious WARN_ONCEs
dma_find_channel and dma_issue_pending_all are good places to warn about
improper api usage. However, warning correctly means synchronizing with
dma_list_mutex, i.e. too much overhead for these fast-path calls.
Reported-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
drivers/dma/dmaengine.c | 6 ------
1 file changed, 6 deletions(-)
(limited to 'drivers/dma/dmaengine.c')
diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c
index 6df144a65fef..a58993011edb 100644
--- a/drivers/dma/dmaengine.c
+++ b/drivers/dma/dmaengine.c
@@ -329,9 +329,6 @@ struct dma_chan *dma_find_channel(enum dma_transaction_type tx_type)
struct dma_chan *chan;
int cpu;
- WARN_ONCE(dmaengine_ref_count == 0,
- "client called %s without a reference", __func__);
-
cpu = get_cpu();
chan = per_cpu_ptr(channel_table[tx_type], cpu)->chan;
put_cpu();
@@ -348,9 +345,6 @@ void dma_issue_pending_all(void)
struct dma_device *device;
struct dma_chan *chan;
- WARN_ONCE(dmaengine_ref_count == 0,
- "client called %s without a reference", __func__);
-
rcu_read_lock();
list_for_each_entry_rcu(device, &dma_device_list, global_node) {
if (dma_has_cap(DMA_PRIVATE, device->cap_mask))
--
cgit