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Message-ID: <27240C0AC20F114CBF8149A2696CBE4A1BFAE8@SHSMSX101.ccr.corp.intel.com>
Date: Thu, 8 Nov 2012 02:07:19 +0000
From: "Liu, Chuansheng" <chuansheng.liu@...el.com>
To: Ming Lei <ming.lei@...onical.com>
CC: "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH V2] firmware loader: Fix the race FW_STATUS_DONE is
followed by class_timeout
> -----Original Message-----
> From: Ming Lei [mailto:ming.lei@...onical.com]
> Sent: Thursday, November 08, 2012 10:02 AM
> To: Liu, Chuansheng
> Cc: gregkh@...uxfoundation.org; linux-kernel@...r.kernel.org
> Subject: Re: [PATCH V2] firmware loader: Fix the race FW_STATUS_DONE is
> followed by class_timeout
>
> On Thu, Nov 8, 2012 at 6:29 PM, Chuansheng Liu <chuansheng.liu@...el.com>
> wrote:
> >
> > There is a race as below when calling request_firmware():
> > CPU1 CPU2
> > write 0 > loading
> > mutex_lock(&fw_lock)
> > ...
> > set_bit FW_STATUS_DONE class_timeout is coming
> > set_bit FW_STATUS_ABORT
> > complete_all &completion
> > ...
> > mutex_unlock(&fw_lock)
> >
> > In this time, the bit FW_STATUS_DONE and FW_STATUS_ABORT are set,
> > and request_firmware() will return failure due to condition in
> > _request_firmware_load():
> > if (!buf->size || test_bit(FW_STATUS_ABORT, &buf->status))
> > retval = -ENOENT;
> >
> > But from the above scenerio, it should be a successful requesting.
> > So we need judge if the bit FW_STATUS_DONE is already set before
> > calling fw_load_abort() in timeout function.
> >
> > As Ming's proposal, we need change the timer into sched_work to
> > benefit from using &fw_lock mutex also.
> >
> > Signed-off-by: liu chuansheng <chuansheng.liu@...el.com>
> > ---
> > drivers/base/firmware_class.c | 25 +++++++++++++++++--------
> > 1 files changed, 17 insertions(+), 8 deletions(-)
> >
> > diff --git a/drivers/base/firmware_class.c b/drivers/base/firmware_class.c
> > index 8945f4e..f2caa0a 100644
> > --- a/drivers/base/firmware_class.c
> > +++ b/drivers/base/firmware_class.c
> > @@ -143,7 +143,7 @@ struct fw_cache_entry {
> > };
> >
> > struct firmware_priv {
> > - struct timer_list timeout;
> > + struct delayed_work timeout_work;
> > bool nowait;
> > struct device dev;
> > struct firmware_buf *buf;
> > @@ -667,10 +667,17 @@ static struct bin_attribute firmware_attr_data = {
> > .write = firmware_data_write,
> > };
> >
> > -static void firmware_class_timeout(u_long data)
> > +static void firmware_class_timeout_work(struct work_struct *work)
> > {
> > - struct firmware_priv *fw_priv = (struct firmware_priv *) data;
> > + struct firmware_priv *fw_priv = container_of(work,
> > + struct firmware_priv, timeout_work.work);
> >
> > + mutex_lock(&fw_lock);
> > + if (test_bit(FW_STATUS_DONE, &(fw_priv->buf->status))) {
> > + mutex_unlock(&fw_lock);
> > + return;
> > + }
> > + mutex_unlock(&fw_lock);
> > fw_load_abort(fw_priv);
>
> fw_lock should be held when fw_load_abort(fw_priv) is running.
OK.
>
> > }
> >
> > @@ -690,8 +697,8 @@ fw_create_instance(struct firmware *firmware,
> const char *fw_name,
> >
> > fw_priv->nowait = nowait;
> > fw_priv->fw = firmware;
> > - setup_timer(&fw_priv->timeout,
> > - firmware_class_timeout, (u_long) fw_priv);
> > + INIT_DELAYED_WORK(&fw_priv->timeout_work,
> > + firmware_class_timeout_work);
> >
> > f_dev = &fw_priv->dev;
> >
> > @@ -858,7 +865,9 @@ static int _request_firmware_load(struct
> firmware_priv *fw_priv, bool uevent,
> > dev_dbg(f_dev->parent, "firmware: direct-loading"
> > " firmware %s\n", buf->fw_id);
> >
> > + mutex_lock(&fw_lock);
> > set_bit(FW_STATUS_DONE, &buf->status);
> > + mutex_unlock(&fw_lock);
> > complete_all(&buf->completion);
> > direct_load = 1;
> > goto handle_fw;
> > @@ -894,15 +903,15 @@ static int _request_firmware_load(struct
> firmware_priv *fw_priv, bool uevent,
> > dev_set_uevent_suppress(f_dev, false);
> > dev_dbg(f_dev, "firmware: requesting %s\n",
> buf->fw_id);
> > if (timeout != MAX_SCHEDULE_TIMEOUT)
> > - mod_timer(&fw_priv->timeout,
> > - round_jiffies_up(jiffies + timeout));
> > +
> schedule_delayed_work(&fw_priv->timeout_work,
> > + timeout * HZ);
>
> timeout is in unit of jiffies already, so multiplying by 'HZ' isn't needed.
Oh, sorry for that, I just tested it in one old version.
Will update the patch soon.
>
> >
> > kobject_uevent(&fw_priv->dev.kobj, KOBJ_ADD);
> > }
> >
> > wait_for_completion(&buf->completion);
> >
> > - del_timer_sync(&fw_priv->timeout);
> > + cancel_delayed_work_sync(&fw_priv->timeout_work);
> >
> > handle_fw:
> > mutex_lock(&fw_lock);
> > --
> > 1.7.0.4
> >
> >
> >
>
> Thanks,
> --
> Ming Lei
--
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