From: Lu Baolu <baolu.lu@linux.intel.com>
To: Mathias Nyman <mathias.nyman@linux.intel.com>,
Baolin Wang <baolin.wang@linaro.org>
Cc: Mathias Nyman <mathias.nyman@intel.com>,
Greg KH <gregkh@linuxfoundation.org>,
USB <linux-usb@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
Mark Brown <broonie@kernel.org>, "Lu, Baolu" <baolu.lu@intel.com>
Subject: Re: [PATCH 2/2] usb: host: xhci: Handle the right timeout command
Date: Wed, 21 Dec 2016 14:57:35 +0800 [thread overview]
Message-ID: <585A27DF.4030003@linux.intel.com> (raw)
In-Reply-To: <58594A9A.10507@linux.intel.com>
Hi Mathias,
I have some comments for the implementation of
xhci_handle_command_timeout() as well.
On 12/20/2016 11:13 PM, Mathias Nyman wrote:
> On 20.12.2016 09:30, Baolin Wang wrote:
> ...
>
> Alright, I gathered all current work related to xhci races and timeouts
> and put them into a branch:
>
> git://git.kernel.org/pub/scm/linux/kernel/git/mnyman/xhci.git timeout_race_fixes
>
> Its based on 4.9
> It includes a few other patches just to avoid conflicts and make my life easier
>
> Interesting patches are:
>
> ee4eb91 xhci: remove unnecessary check for pending timer
> 0cba67d xhci: detect stop endpoint race using pending timer instead of counter.
> 4f2535f xhci: Handle command completion and timeout race
> b9d00d7 usb: host: xhci: Fix possible wild pointer when handling abort command
> 529a5a0 usb: xhci: fix possible wild pointer
> 4766555 xhci: Fix race related to abort operation
> de834a3 xhci: Use delayed_work instead of timer for command timeout
> 69973b8 Linux 4.9
>
> The fixes for command queue races will go to usb-linus and stable, the
> reworks for stop ep watchdog timer will go to usb-next.
>
> Still completely untested, (well it compiles)
>
> Felipe gave instructions how to modify dwc3 driver to timeout on address
> devicecommands to test these, I'll try to set that up.
>
> All additional testing is welcome, especially if you can trigger timeouts
> and races
>
> -Mathias
>
>
I post the code below and add my comments in line.
1276 void xhci_handle_command_timeout(struct work_struct *work)
1277 {
1278 struct xhci_hcd *xhci;
1279 int ret;
1280 unsigned long flags;
1281 u64 hw_ring_state;
1282
1283 xhci = container_of(to_delayed_work(work), struct xhci_hcd, cmd_timer);
1284
1285 spin_lock_irqsave(&xhci->lock, flags);
1286
1287 /*
1288 * If timeout work is pending, or current_cmd is NULL, it means we
1289 * raced with command completion. Command is handled so just return.
1290 */
1291 if (!xhci->current_cmd || delayed_work_pending(&xhci->cmd_timer)) {
1292 spin_unlock_irqrestore(&xhci->lock, flags);
1293 return;
1294 }
1295 /* mark this command to be cancelled */
1296 xhci->current_cmd->status = COMP_CMD_ABORT;
1297
1298 /* Make sure command ring is running before aborting it */
1299 hw_ring_state = xhci_read_64(xhci, &xhci->op_regs->cmd_ring);
1300 if ((xhci->cmd_ring_state & CMD_RING_STATE_RUNNING) &&
1301 (hw_ring_state & CMD_RING_RUNNING)) {
1302 /* Prevent new doorbell, and start command abort */
1303 xhci->cmd_ring_state = CMD_RING_STATE_ABORTED;
1304 spin_unlock_irqrestore(&xhci->lock, flags);
1305 xhci_dbg(xhci, "Command timeout\n");
1306 ret = xhci_abort_cmd_ring(xhci);
1307 if (unlikely(ret == -ESHUTDOWN)) {
1308 xhci_err(xhci, "Abort command ring failed\n");
1309 xhci_cleanup_command_queue(xhci);
1310 usb_hc_died(xhci_to_hcd(xhci)->primary_hcd);
1311 xhci_dbg(xhci, "xHCI host controller is dead.\n");
1312 }
1313 return;
1314 }
1315
1316 /* host removed. Bail out */
1317 if (xhci->xhc_state & XHCI_STATE_REMOVING) {
1318 spin_unlock_irqrestore(&xhci->lock, flags);
1319 xhci_dbg(xhci, "host removed, ring start fail?\n");
1320 xhci_cleanup_command_queue(xhci);
1321 return;
1322 }
I think this part of code should be moved up to line 1295.
1323
1324 /* command timeout on stopped ring, ring can't be aborted */
1325 xhci_dbg(xhci, "Command timeout on stopped ring\n");
1326 xhci_handle_stopped_cmd_ring(xhci, xhci->current_cmd);
1327 spin_unlock_irqrestore(&xhci->lock, flags);
This part of code is tricky. I have no idea about in which case should this
code be executed? Anyway, we shouldn't call xhci_handle_stopped_cmd_ring()
here, right?
1328 return;
1329 }
Best regards,
Lu Baolu
next prev parent reply other threads:[~2016-12-21 6:57 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-12-05 7:51 [PATCH 1/2] usb: host: xhci: Fix possible wild pointer when handling abort command Baolin Wang
2016-12-05 7:51 ` [PATCH 2/2] usb: host: xhci: Handle the right timeout command Baolin Wang
2016-12-12 15:52 ` Mathias Nyman
2016-12-13 3:21 ` Baolin Wang
2016-12-19 10:33 ` Mathias Nyman
2016-12-19 11:34 ` Baolin Wang
2016-12-19 12:13 ` Mathias Nyman
2016-12-20 3:23 ` Baolin Wang
2016-12-20 4:29 ` Lu Baolu
2016-12-20 6:06 ` Baolin Wang
2016-12-20 6:39 ` Lu Baolu
2016-12-20 6:46 ` Baolin Wang
2016-12-20 7:18 ` Lu Baolu
2016-12-20 7:30 ` Baolin Wang
2016-12-20 15:13 ` Mathias Nyman
2016-12-21 2:22 ` Baolin Wang
2016-12-21 13:00 ` Mathias Nyman
2016-12-27 3:07 ` Baolin Wang
2017-01-02 14:57 ` Mathias Nyman
2017-01-03 6:20 ` Baolin Wang
2016-12-21 6:17 ` Lu Baolu
2016-12-21 12:48 ` Mathias Nyman
2016-12-21 14:10 ` OGAWA Hirofumi
2016-12-21 15:04 ` Mathias Nyman
2016-12-21 15:18 ` OGAWA Hirofumi
2016-12-22 1:46 ` Lu Baolu
2016-12-23 12:54 ` Mathias Nyman
2016-12-22 1:43 ` Lu Baolu
2016-12-21 6:57 ` Lu Baolu [this message]
2016-12-21 12:57 ` Mathias Nyman
2016-12-22 1:39 ` Lu Baolu
2016-12-05 14:08 ` [PATCH 1/2] usb: host: xhci: Fix possible wild pointer when handling abort command Mathias Nyman
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