@@ -139,30 +139,43 @@ MODULE_PARM_DESC(usbfs_memory_mb,
/* Hard limit, necessary to avoid arithmetic overflow */
#define USBFS_XFER_MAX (UINT_MAX / 2 - 1000000)
-static atomic64_t usbfs_memory_usage; /* Total memory currently allocated */
+static DEFINE_SPINLOCK(usbfs_memory_usage_lock);
+static u64 usbfs_memory_usage; /* Total memory currently allocated */
/* Check whether it's okay to allocate more memory for a transfer */
static int usbfs_increase_memory_usage(u64 amount)
{
- u64 lim;
+ u64 lim, total_mem;
+ unsigned long flags;
+ int ret;
- lim = READ_ONCE(usbfs_memory_mb);
+ lim = usbfs_memory_mb;
lim <<= 20;
- atomic64_add(amount, &usbfs_memory_usage);
-
- if (lim > 0 && atomic64_read(&usbfs_memory_usage) > lim) {
- atomic64_sub(amount, &usbfs_memory_usage);
- return -ENOMEM;
- }
+ ret = 0;
+ spin_lock_irqsave(&usbfs_memory_usage_lock, flags);
+ total_mem = usbfs_memory_usage + amount;
+ if (lim > 0 && total_mem > lim)
+ ret = -ENOMEM;
+ else
+ usbfs_memory_usage = total_mem;
+ spin_unlock_irqrestore(&usbfs_memory_usage_lock, flags);
- return 0;
+ return ret;
}
/* Memory for a transfer is being deallocated */
static void usbfs_decrease_memory_usage(u64 amount)
{
- atomic64_sub(amount, &usbfs_memory_usage);
+ u64 total_mem;
+ unsigned long flags;
+
+ spin_lock_irqsave(&usbfs_memory_usage_lock, flags);
+ total_mem = usbfs_memory_usage;
+ if (amount > total_mem)
+ amount = total_mem;
+ usbfs_memory_usage = total_mem - amount;
+ spin_unlock_irqrestore(&usbfs_memory_usage_lock, flags);
}
static int connected(struct usb_dev_state *ps)
While the fromer code imposes a limit on the used memory, it might be over pessimistic (even if this is unlikely). Example scenario: 8 threads running in parallel, all entering "usbfs_increase_memory_usage()" at the same time. The atomic accesses in "usbfs_increase_memory_usage()" could be serialized like this: 8 x "atomic64_add" 8 x "atomic64_read" If the 8 x "atomic64_add" raise "usbfs_memory_usage" above the limit, then all 8 calls of "usbfs_increase_memory_usage()" will return with -ENOMEM. If you instead serialize over the whole access to "usbfs_memory_usage" by using a spinlock, some of these calls will succeed. Signed-off-by: Ingo Rohloff <ingo.rohloff@lauterbach.com> --- drivers/usb/core/devio.c | 35 ++++++++++++++++++++++++----------- 1 file changed, 24 insertions(+), 11 deletions(-)