Hi,
Robert Jarzmik wrote:
Antonio Ospite <ospite@xxxxxxxxxxxxxxxxx> writes:
With your latest patch on top of 2.6.32 I get the "possible recursive
locking" message at the *first* cable unplug/plug cycle, I am appending
it here, the log is partial because I dumped it from RAM and something
was lost.
Thanks.
Now, lets have another try. This patch is a bit saner, and though I got the
"locking detected" you noticed without it, I didn't manage to get it with this
patch applied.
As your test platform is far better than mine, would you mind a bit of testing
... again. This patch applies on top of v2.6.32.
Cheers.
--
Robert
>From 3ca70f842651f607790a2ff94f2b3a7ec223196d Mon Sep 17 00:00:00 2001
From: Robert Jarzmik <robert.jarzmik@xxxxxxx>
Date: Sat, 12 Dec 2009 15:13:24 +0100
Subject: [PATCH] pxa27x_udc: Fix deadlocks on request queueing
As reported by Antonio, there are cases where the ep->lock
can be taken twice, triggering a deadlock.
The typical sequence is :
irq_handler
\
-> gadget.complete()
\
-> pxa27x_udc.pxa_ep_queue() : ep->lock is taken
\
-> gadget.complete()
\
-> pxa27x_udc.pxa_ep_queue() : ep->lock is taken
==> *deadlock*
The patch fixes this by :
- releasing the lock each time gadget.complete() is called
- adding a check in handle_ep() to detect a recursive call,
in which case the function becomes on no-op.
The patch is still not good enough for ep0. For this unique
endpoint, another well thought over patch will be needed.
Reported-by: Antonio Ospite <ospite@xxxxxxxxxxxxxxxxx>
Signed-off-by: Robert Jarzmik <robert.jarzmik@xxxxxxx>
---
drivers/usb/gadget/pxa27x_udc.c | 114 +++++++++++++++++++++++++++------------
drivers/usb/gadget/pxa27x_udc.h | 6 ++
2 files changed, 85 insertions(+), 35 deletions(-)
+ /* don't modify queue heads during completion callback */
+ if (spin_is_locked(&ep->lock)) {
+ spin_unlock(&ep->lock);
+ req->req.complete(&req->udc_usb_ep->usb_ep, &req->req);
+ spin_lock(&ep->lock);
+ } else
+ req->req.complete(&req->udc_usb_ep->usb_ep, &req->req);
}
I have fixed in the same way without pass the flag
Michael
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