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Message-ID: <ZxtShfshsuyVzGx3@hu-mojha-hyd.qualcomm.com>
Date: Fri, 25 Oct 2024 13:40:45 +0530
From: Mukesh Ojha <quic_mojha@...cinc.com>
To: Mathieu Poirier <mathieu.poirier@...aro.org>
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 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.
[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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