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Message-ID: <Zxu0U9U+BvTo20Zq@p14s>
Date: Fri, 25 Oct 2024 09:08:03 -0600
From: Mathieu Poirier <mathieu.poirier@...aro.org>
To: Mukesh Ojha <quic_mojha@...cinc.com>
Cc: Bjorn Andersson <andersson@...nel.org>,
linux-remoteproc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] remoteproc: Add a new remoteproc state RPROC_DEFUNCT
On Fri, Oct 25, 2024 at 01:40:45PM +0530, Mukesh Ojha wrote:
> On Mon, Oct 21, 2024 at 09:12:47AM -0600, Mathieu Poirier wrote:
> > Hi Mukesh,
> >
> > On Wed, Oct 16, 2024 at 10:25:46AM +0530, Mukesh Ojha wrote:
> > > Multiple call to glink_subdev_stop() for the same remoteproc can happen
> > > if rproc_stop() fails from Process-A that leaves the rproc state to
> > > RPROC_CRASHED state later a call to recovery_store from user space in
> > > Process B triggers rproc_trigger_recovery() of the same remoteproc to
> > > recover it results in NULL pointer dereference issue in
> > > qcom_glink_smem_unregister().
> > >
> > > There is other side to this issue if we want to fix this via adding a
> > > NULL check on glink->edge which does not guarantees that the remoteproc
> > > will recover in second call from Process B as it has failed in the first
> > > Process A during SMC shutdown call and may again fail at the same call
> > > and rproc can not recover for such case.
> > >
> > > Add a new rproc state RPROC_DEFUNCT i.e., non recoverable state of
> > > remoteproc and the only way to recover from it via system restart.
> > >
> > > Process-A Process-B
> > >
> > > fatal error interrupt happens
> > >
> > > rproc_crash_handler_work()
> > > mutex_lock_interruptible(&rproc->lock);
> > > ...
> > >
> > > rproc->state = RPROC_CRASHED;
> > > ...
> > > mutex_unlock(&rproc->lock);
> > >
> > > rproc_trigger_recovery()
> > > mutex_lock_interruptible(&rproc->lock);
> > >
> > > adsp_stop()
> > > qcom_q6v5_pas 20c00000.remoteproc: failed to shutdown: -22
> > > remoteproc remoteproc3: can't stop rproc: -22
> > > mutex_unlock(&rproc->lock);
> >
> > Ok, that can happen.
> >
> > >
> > > echo enabled > /sys/class/remoteproc/remoteprocX/recovery
> > > recovery_store()
> > > rproc_trigger_recovery()
> > > mutex_lock_interruptible(&rproc->lock);
> > > rproc_stop()
> > > glink_subdev_stop()
> > > qcom_glink_smem_unregister() ==|
> > > |
> > > V
> >
> > I am missing some information here but I will _assume_ this is caused by
> > glink->edge being set to NULL [1] when glink_subdev_stop() is first called by
> > process A. Instead of adding a new state to the core I think a better idea
> > would be to add a check for a NULL value on @smem in
> > qcom_glink_smem_unregister(). This is a problem that should be fixed in the
> > driver rather than the core.
> >
> > [1]. https://elixir.bootlin.com/linux/v6.12-rc4/source/drivers/remoteproc/qcom_common.c#L213
>
>
> I did the same here [1] but after discussion with Bjorn, realized that
> remoteproc might not even recover and may fail in the second attempt as
> well and only way is reboot of the machine.
Whether in RPROC_CRASHED or RPROC_DEFUNCT state, the end result is the same -
manual intervention is needed. I don't see why another state needs to be added.
>
> [1]
> https://lore.kernel.org/lkml/20240925103351.1628788-1-quic_mojha@quicinc.com/
>
> >
> > > Unable to handle kernel NULL pointer dereference
> > > at virtual address 0000000000000358
> > >
> > > Signed-off-by: Mukesh Ojha <quic_mojha@...cinc.com>
> > > ---
> > > Changes in v3:
> > > - Fix kernel test reported error.
> > >
> > > Changes in v2:
> > > - Removed NULL pointer check instead added a new state to signify
> > > non-recoverable state of remoteproc.
> > >
> > > drivers/remoteproc/remoteproc_core.c | 3 ++-
> > > drivers/remoteproc/remoteproc_sysfs.c | 1 +
> > > include/linux/remoteproc.h | 5 ++++-
> > > 3 files changed, 7 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/drivers/remoteproc/remoteproc_core.c b/drivers/remoteproc/remoteproc_core.c
> > > index f276956f2c5c..c4e14503b971 100644
> > > --- a/drivers/remoteproc/remoteproc_core.c
> > > +++ b/drivers/remoteproc/remoteproc_core.c
> > > @@ -1727,6 +1727,7 @@ static int rproc_stop(struct rproc *rproc, bool crashed)
> > > /* power off the remote processor */
> > > ret = rproc->ops->stop(rproc);
> > > if (ret) {
> > > + rproc->state = RPROC_DEFUNCT;
> > > dev_err(dev, "can't stop rproc: %d\n", ret);
> > > return ret;
> > > }
> > > @@ -1839,7 +1840,7 @@ int rproc_trigger_recovery(struct rproc *rproc)
> > > return ret;
> > >
> > > /* State could have changed before we got the mutex */
> > > - if (rproc->state != RPROC_CRASHED)
> > > + if (rproc->state == RPROC_DEFUNCT || rproc->state != RPROC_CRASHED)
> > > goto unlock_mutex;
> >
> > The problem is that rproc_trigger_recovery() an only be called once for a
> > remoteproc, something that modifies the state machine and may introduce backward
> > compatibility issues for other remote processor implementations.
> >
>
> I missed one more point to add here which i tried to highlight in second
> version[2] that setting of RPROC_DEFUNCT should happen for this case
> from vendor remoteproc driver and not at the core and that should take
> care of the backward compatibility.
>
> [2]
> https://lore.kernel.org/lkml/Zw2CAbMozI8vu4SL@hu-mojha-hyd.qualcomm.com/
>
> -Mukesh
>
> > Thanks,
> > Mathieu
> >
> > >
> > > dev_err(dev, "recovering %s\n", rproc->name);
> > > diff --git a/drivers/remoteproc/remoteproc_sysfs.c b/drivers/remoteproc/remoteproc_sysfs.c
> > > index 138e752c5e4e..5f722b4576b2 100644
> > > --- a/drivers/remoteproc/remoteproc_sysfs.c
> > > +++ b/drivers/remoteproc/remoteproc_sysfs.c
> > > @@ -171,6 +171,7 @@ static const char * const rproc_state_string[] = {
> > > [RPROC_DELETED] = "deleted",
> > > [RPROC_ATTACHED] = "attached",
> > > [RPROC_DETACHED] = "detached",
> > > + [RPROC_DEFUNCT] = "defunct",
> > > [RPROC_LAST] = "invalid",
> > > };
> > >
> > > diff --git a/include/linux/remoteproc.h b/include/linux/remoteproc.h
> > > index b4795698d8c2..3e4ba06c6a9a 100644
> > > --- a/include/linux/remoteproc.h
> > > +++ b/include/linux/remoteproc.h
> > > @@ -417,6 +417,8 @@ struct rproc_ops {
> > > * has attached to it
> > > * @RPROC_DETACHED: device has been booted by another entity and waiting
> > > * for the core to attach to it
> > > + * @RPROC_DEFUNCT: device neither crashed nor responding to any of the
> > > + * requests and can only recover on system restart.
> > > * @RPROC_LAST: just keep this one at the end
> > > *
> > > * Please note that the values of these states are used as indices
> > > @@ -433,7 +435,8 @@ enum rproc_state {
> > > RPROC_DELETED = 4,
> > > RPROC_ATTACHED = 5,
> > > RPROC_DETACHED = 6,
> > > - RPROC_LAST = 7,
> > > + RPROC_DEFUNCT = 7,
> > > + RPROC_LAST = 8,
> > > };
> > >
> > > /**
> > > --
> > > 2.34.1
> > >
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