USB: usbtest: avoid to free coherent buffer in atomic context

This patch fixes the warning below:
[30753.755998] ------------[ cut here ]------------
[30753.755998] WARNING: at /home/tom/git/linux-2.6/linux-2.6-next/arch/x86/include/asm/dma-mapping.h:155 hcd_buffer_free+0xb1/0xd4 [usbcore]()
[30753.755998] Hardware name: 6475EK2
[30753.755998] Modules linked in: uvcvideo ehci_hcd usbtest cdc_ether usbnet vfat fat usb_storage nfsd lockd nfs_acl auth_rpcgss exportfs mii tun videodev v4l1_compat v4l2_compat_ioctl32 fuse bridge stp llc sunrpc ipv6 cpufreq_ondemand acpi_cpufreq freq_table mperf kvm_intel kvm arc4 ecb ath5k usbhid mac80211 snd_hda_codec_conexant ch341 usbserial ath cfg80211 thinkpad_acpi snd_hda_intel pcspkr wmi hwmon yenta_socket iTCO_wdt iTCO_vendor_support i2c_i801 e1000e snd_hda_codec snd_hwdep snd_pcm snd_timer snd soundcore snd_page_alloc pata_acpi uhci_hcd ohci_hcd usbcore i915 drm_kms_helper drm i2c_algo_bit i2c_core video output [last unloaded: uvcvideo]
[30753.755998] Pid: 0, comm: swapper Tainted: G        W   2.6.35-rc6-gkh-wl+ #49
[30753.755998] Call Trace:
[30753.755998]  <IRQ>  [<ffffffff8104478a>] warn_slowpath_common+0x80/0x98
[30753.755998]  [<ffffffff810447b7>] warn_slowpath_null+0x15/0x17
[30753.755998]  [<ffffffffa00ce02d>] hcd_buffer_free+0xb1/0xd4 [usbcore]
[30753.755998]  [<ffffffffa00c1345>] usb_free_coherent+0x1c/0x1e [usbcore]
[30753.755998]  [<ffffffffa00b13e4>] simple_free_urb+0x23/0x2f [usbtest]
[30753.755998]  [<ffffffffa00b210b>] iso_callback+0xbb/0x10f [usbtest]
[30753.755998]  [<ffffffffa00c7390>] usb_hcd_giveback_urb+0x8c/0xc0 [usbcore]
[30753.755998]  [<ffffffffa0449b35>] ehci_urb_done+0x84/0x95 [ehci_hcd]
[30753.755998]  [<ffffffffa044b5a5>] ehci_work+0x41a/0x7dd [ehci_hcd]
[30753.755998]  [<ffffffffa044e298>] ehci_irq+0x33b/0x370 [ehci_hcd]
[30753.755998]  [<ffffffff8100fb05>] ? sched_clock+0x9/0xd
[30753.755998]  [<ffffffff8105e641>] ? sched_clock_local+0x1c/0x82
[30753.755998]  [<ffffffff8105e76a>] ? sched_clock_cpu+0xc3/0xce
[30753.755998]  [<ffffffff81067c7e>] ? trace_hardirqs_off+0xd/0xf
[30753.755998]  [<ffffffff8105e7b8>] ? cpu_clock+0x43/0x5e
[30753.755998]  [<ffffffffa00c6999>] usb_hcd_irq+0x45/0xa1 [usbcore]
[30753.755998]  [<ffffffff81092e02>] handle_IRQ_event+0x20/0xa5
[30753.755998]  [<ffffffff81094cea>] handle_fasteoi_irq+0x92/0xd2
[30753.755998]  [<ffffffff8100c0ed>] handle_irq+0x1f/0x2a
[30753.755998]  [<ffffffff8100b75d>] do_IRQ+0x57/0xbe
[30753.755998]  [<ffffffff8136a693>] ret_from_intr+0x0/0x16
[30753.755998]  <EOI>  [<ffffffff81223baa>] ? acpi_idle_enter_bm+0x231/0x269
[30753.755998]  [<ffffffff81223ba3>] ? acpi_idle_enter_bm+0x22a/0x269
[30753.755998]  [<ffffffff812c4b6b>] cpuidle_idle_call+0x99/0xce
[30753.755998]  [<ffffffff81008dd5>] cpu_idle+0x61/0xaa
[30753.755998]  [<ffffffff8136374b>] start_secondary+0x1c2/0x1c6
[30753.755998] ---[ end trace 904cfaf7ab4cb1a2 ]---

Signed-off-by: Ming Lei <tom.leiming@gmail.com>
Cc: stable <stable@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/misc/usbtest.c

@@ -1378,7 +1378,6 @@ static void iso_callback (struct urb *urb)
 			break;
 		}
 	}
-	simple_free_urb (urb);
 
 	ctx->pending--;
 	if (ctx->pending == 0) {
@@ -1495,6 +1494,7 @@ test_iso_queue (struct usbtest_dev *dev, struct usbtest_param *param,
 			}
 
 			simple_free_urb (urbs [i]);
+			urbs[i] = NULL;
 			context.pending--;
 			context.submit_error = 1;
 			break;
@@ -1504,6 +1504,10 @@ test_iso_queue (struct usbtest_dev *dev, struct usbtest_param *param,
 
 	wait_for_completion (&context.done);
 
+	for (i = 0; i < param->sglen; i++) {
+		if (urbs[i])
+			simple_free_urb(urbs[i]);
+	}
 	/*
 	 * Isochronous transfers are expected to fail sometimes.  As an
 	 * arbitrary limit, we will report an error if any submissions