This patch kills atomic_inc/atomic_dec operations on
urb->use_count in URB submit/complete path.
The urb->use_count is only used for unlinking URB, and it isn't
necessary defined as atomic counter, so the variable is renamed
as urb->use_flag for this purpose, then reading/writing the
flag is still kept as atomic but ARCH's atomic operations(atomic_inc/
atomic_dec) are saved.
Cc: Oliver Neukum <oliver@xxxxxxxxxx>
Cc: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxxxxx>
---
drivers/usb/core/hcd.c | 14 +++++++++-----
drivers/usb/core/urb.c | 8 ++++++--
drivers/usb/core/usb.h | 5 +++++
include/linux/usb.h | 2 +-
4 files changed, 21 insertions(+), 8 deletions(-)
diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c
index 0b4d1ae..9457c4e 100644
--- a/drivers/usb/core/hcd.c
+++ b/drivers/usb/core/hcd.c
@@ -1555,7 +1555,7 @@ int usb_hcd_submit_urb (struct urb *urb, gfp_t mem_flags)
* an error or calls giveback(), but not both.
*/
usb_get_urb(urb);
- atomic_inc(&urb->use_count);
+ atomic_set(&urb->use_flag, URB_USING);
this_cpu_inc(*urb->dev->urbnum);
usbmon_urb_submit(&hcd->self, urb);
@@ -1582,7 +1582,7 @@ int usb_hcd_submit_urb (struct urb *urb, gfp_t mem_flags)
usbmon_urb_submit_error(&hcd->self, urb, status);
urb->hcpriv = NULL;
INIT_LIST_HEAD(&urb->urb_list);
- atomic_dec(&urb->use_count);
+ atomic_set(&urb->use_flag, URB_UNUSED);
this_cpu_dec(*urb->dev->urbnum);
if (atomic_read(&urb->reject))
wake_up(&usb_kill_urb_queue);
@@ -1628,11 +1628,11 @@ int usb_hcd_unlink_urb (struct urb *urb, int status)
/* Prevent the device and bus from going away while
* the unlink is carried out. If they are already gone
- * then urb->use_count must be 0, since disconnected
+ * then urb->use_flag must be URB_UNUSED, since disconnected
* devices can't have any active URBs.
*/
spin_lock_irqsave(&hcd_urb_unlink_lock, flags);
- if (atomic_read(&urb->use_count) > 0) {
+ if (atomic_read(&urb->use_flag) != URB_UNUSED) {
retval = 0;
usb_get_dev(urb->dev);
}
@@ -1672,6 +1672,8 @@ static void __usb_hcd_giveback_urb(struct urb *urb)
/* pass ownership to the completion handler */
urb->status = status;
+ atomic_set(&urb->use_flag, URB_UNUSING);
+
/*
* We disable local IRQs here avoid possible deadlock because
* drivers may call spin_lock() to hold lock which might be
@@ -1686,7 +1688,9 @@ static void __usb_hcd_giveback_urb(struct urb *urb)
urb->complete(urb);
local_irq_restore(flags);
- atomic_dec(&urb->use_count);
+ if (atomic_read(&urb->use_flag) == URB_UNUSING)
+ atomic_set(&urb->use_flag, URB_UNUSED);
+
if (unlikely(atomic_read(&urb->reject)))
wake_up(&usb_kill_urb_queue);
usb_put_urb(urb);
diff --git a/drivers/usb/core/urb.c b/drivers/usb/core/urb.c
index c12bc79..79d2534 100644
--- a/drivers/usb/core/urb.c
+++ b/drivers/usb/core/urb.c
@@ -9,6 +9,8 @@
#include <linux/usb/hcd.h>
#include <linux/scatterlist.h>
+#include "usb.h"
+
#define to_urb(d) container_of(d, struct urb, kref)
@@ -661,7 +663,8 @@ void usb_kill_urb(struct urb *urb)
atomic_inc(&urb->reject);
usb_hcd_unlink_urb(urb, -ENOENT);
- wait_event(usb_kill_urb_queue, atomic_read(&urb->use_count) == 0);
+ wait_event(usb_kill_urb_queue,
+ atomic_read(&urb->use_flag) == URB_UNUSED);
atomic_dec(&urb->reject);
}
@@ -705,7 +708,8 @@ void usb_poison_urb(struct urb *urb)
return;
usb_hcd_unlink_urb(urb, -ENOENT);
- wait_event(usb_kill_urb_queue, atomic_read(&urb->use_count) == 0);
+ wait_event(usb_kill_urb_queue,
+ atomic_read(&urb->use_flag) == URB_UNUSED);
}
EXPORT_SYMBOL_GPL(usb_poison_urb);
diff --git a/drivers/usb/core/usb.h b/drivers/usb/core/usb.h
index 12a0181..bbdcf93 100644
--- a/drivers/usb/core/usb.h
+++ b/drivers/usb/core/usb.h
@@ -5,6 +5,11 @@
struct usb_hub_descriptor;
struct dev_state;
+/* urb use flag*/
+#define URB_UNUSED 0
+#define URB_USING 1
+#define URB_UNUSING 2
+
/* Functions local to drivers/usb/core/ */
extern int usb_create_sysfs_dev_files(struct usb_device *dev);
diff --git a/include/linux/usb.h b/include/linux/usb.h
index 75332dc..7f5f629 100644
--- a/include/linux/usb.h
+++ b/include/linux/usb.h
@@ -1408,7 +1408,7 @@ struct urb {
/* private: usb core and host controller only fields in the urb */
struct kref kref; /* reference count of the URB */
void *hcpriv; /* private data for host controller */
- atomic_t use_count; /* concurrent submissions counter */
+ atomic_t use_flag; /* urb using flag */
atomic_t reject; /* submissions will fail */
int unlinked; /* unlink error code */
--
1.7.9.5
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