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Subject: Re: [REGRESSION] "USB: use kfifo to buffer usb-generic serial
 writes" causes gobi_loader to hang
From: Marcel Holtmann <marcel@holtmann.org>
To: Matthew Garrett <mjg59@srcf.ucam.org>
Cc: dvomlehn@cisco.com, gregkh@suse.de, linux-usb-devel@lists.sourceforge.net,
       linux-kernel@vger.kernel.org
In-Reply-To: <20100117025535.GB7045@srcf.ucam.org>
References: <20100117025535.GB7045@srcf.ucam.org>
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Date: Sun, 17 Jan 2010 00:13:33 -0800
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Hi Matthew,

> gobi_loader writes firmware to gobi USB devices (qcserial) via the USB 
> serial layer by writing it a megabyte at a time (matching the Windows 
> driver behaviour). Commit 8e8dce065088833fc418bfa5fbf035cb0726c04c 
> breaks it - strace shows the write simply hanging. ssyrq-t says the 
> backtrace is:
> 
> Jan 17 15:37:37 localhost kernel: Call Trace:
> Jan 17 15:37:37 localhost kernel: [<ffffffff8128986c>] n_tty_write+0x2da/0x351
> Jan 17 15:37:37 localhost kernel: [<ffffffff810464b4>] ? default_wake_function+0x0/0x14
> Jan 17 15:37:37 localhost kernel: [<ffffffff81286969>] tty_write+0x19d/0x245
> Jan 17 15:37:37 localhost kernel: [<ffffffff81289592>] ? n_tty_write+0x0/0x351
> Jan 17 15:37:37 localhost kernel: [<ffffffff81103e44>] vfs_write+0xae/0x10b
> Jan 17 15:37:37 localhost kernel: [<ffffffff81103f61>] sys_write+0x4a/0x6e
> Jan 17 15:37:37 localhost kernel: [<ffffffff81009e45>] tracesys+0xd9/0xde
> 
> The commit before this works fine.

maybe I should have finished my libusb version of the gobi_loader ;)

Regards

Marcel