* [PATCH] dmaengine: Remove a useless mutex
@ 2022-02-06 9:47 Christophe JAILLET
2022-04-11 14:22 ` Vinod Koul
0 siblings, 1 reply; 2+ messages in thread
From: Christophe JAILLET @ 2022-02-06 9:47 UTC (permalink / raw)
To: Vinod Koul; +Cc: linux-kernel, kernel-janitors, Christophe JAILLET, dmaengine
According to lib/idr.c,
The IDA handles its own locking. It is safe to call any of the IDA
functions without synchronisation in your code.
so the 'chan_mutex' mutex can just be removed.
It is here only to protect some ida_alloc()/ida_free() calls.
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
---
Un-tested
---
drivers/dma/dmaengine.c | 7 -------
include/linux/dmaengine.h | 1 -
2 files changed, 8 deletions(-)
diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c
index 2cfa8458b51b..e80feeea0e01 100644
--- a/drivers/dma/dmaengine.c
+++ b/drivers/dma/dmaengine.c
@@ -1053,9 +1053,7 @@ static int __dma_async_device_channel_register(struct dma_device *device,
* When the chan_id is a negative value, we are dynamically adding
* the channel. Otherwise we are static enumerating.
*/
- mutex_lock(&device->chan_mutex);
chan->chan_id = ida_alloc(&device->chan_ida, GFP_KERNEL);
- mutex_unlock(&device->chan_mutex);
if (chan->chan_id < 0) {
pr_err("%s: unable to alloc ida for chan: %d\n",
__func__, chan->chan_id);
@@ -1078,9 +1076,7 @@ static int __dma_async_device_channel_register(struct dma_device *device,
return 0;
err_out_ida:
- mutex_lock(&device->chan_mutex);
ida_free(&device->chan_ida, chan->chan_id);
- mutex_unlock(&device->chan_mutex);
err_free_dev:
kfree(chan->dev);
err_free_local:
@@ -1113,9 +1109,7 @@ static void __dma_async_device_channel_unregister(struct dma_device *device,
device->chancnt--;
chan->dev->chan = NULL;
mutex_unlock(&dma_list_mutex);
- mutex_lock(&device->chan_mutex);
ida_free(&device->chan_ida, chan->chan_id);
- mutex_unlock(&device->chan_mutex);
device_unregister(&chan->dev->device);
free_percpu(chan->local);
}
@@ -1250,7 +1244,6 @@ int dma_async_device_register(struct dma_device *device)
if (rc != 0)
return rc;
- mutex_init(&device->chan_mutex);
ida_init(&device->chan_ida);
/* represent channels in sysfs. Probably want devs too */
diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
index 842d4f7ca752..6db9e03afd0b 100644
--- a/include/linux/dmaengine.h
+++ b/include/linux/dmaengine.h
@@ -870,7 +870,6 @@ struct dma_device {
struct device *dev;
struct module *owner;
struct ida chan_ida;
- struct mutex chan_mutex; /* to protect chan_ida */
u32 src_addr_widths;
u32 dst_addr_widths;
--
2.32.0
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] dmaengine: Remove a useless mutex
2022-02-06 9:47 [PATCH] dmaengine: Remove a useless mutex Christophe JAILLET
@ 2022-04-11 14:22 ` Vinod Koul
0 siblings, 0 replies; 2+ messages in thread
From: Vinod Koul @ 2022-04-11 14:22 UTC (permalink / raw)
To: Christophe JAILLET; +Cc: linux-kernel, kernel-janitors, dmaengine
On 06-02-22, 10:47, Christophe JAILLET wrote:
> According to lib/idr.c,
> The IDA handles its own locking. It is safe to call any of the IDA
> functions without synchronisation in your code.
>
> so the 'chan_mutex' mutex can just be removed.
> It is here only to protect some ida_alloc()/ida_free() calls.
Applied, thanks
--
~Vinod
^ permalink raw reply [flat|nested] 2+ messages in thread
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