linux-kernel - Re: [PATCH] remoteproc: core: Remove state checking before changing state

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Date:   Fri, 25 Mar 2022 03:44:20 +0000
From:   "S.J. Wang" <shengjiu.wang@....com>
To:     Mathieu Poirier <mathieu.poirier@...aro.org>
CC:     "bjorn.andersson@...aro.org" <bjorn.andersson@...aro.org>,
        "linux-remoteproc@...r.kernel.org" <linux-remoteproc@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "shengjiu.wang@...il.com" <shengjiu.wang@...il.com>
Subject: Re: [PATCH] remoteproc: core: Remove state checking before changing
 state

Hi

> >
> > There is no mutex protecting of these state checking, which can't
> > garantee there is no another instance is trying to do same operation.
> >
> > The reference counter rproc->power is used to manage state changing
> > and there is mutex protection in each operation function for multi
> > instance case.
> >
> > So remove this state checking in rproc_cdev_write() and state_store(),
> > just let reference counter rproc->power to manage the behaviors.
> >
> > Signed-off-by: Shengjiu Wang <shengjiu.wang@....com>
> > ---
> >  drivers/remoteproc/remoteproc_cdev.c  | 11 -----------
> > drivers/remoteproc/remoteproc_sysfs.c | 11 -----------
> >  2 files changed, 22 deletions(-)
> >
> > diff --git a/drivers/remoteproc/remoteproc_cdev.c
> > b/drivers/remoteproc/remoteproc_cdev.c
> > index 906ff3c4dfdd..687f205fd70a 100644
> > --- a/drivers/remoteproc/remoteproc_cdev.c
> > +++ b/drivers/remoteproc/remoteproc_cdev.c
> > @@ -32,21 +32,10 @@ static ssize_t rproc_cdev_write(struct file *filp,
> const char __user *buf, size_
> >                 return -EFAULT;
> >
> >         if (!strncmp(cmd, "start", len)) {
> > -               if (rproc->state == RPROC_RUNNING ||
> > -                   rproc->state == RPROC_ATTACHED)
> > -                       return -EBUSY;
> > -
> >                 ret = rproc_boot(rproc);
> >         } else if (!strncmp(cmd, "stop", len)) {
> > -               if (rproc->state != RPROC_RUNNING &&
> > -                   rproc->state != RPROC_ATTACHED)
> > -                       return -EINVAL;
> > -
> >                 ret = rproc_shutdown(rproc);
> >         } else if (!strncmp(cmd, "detach", len)) {
> > -               if (rproc->state != RPROC_ATTACHED)
> > -                       return -EINVAL;
> > -
> >                 ret = rproc_detach(rproc);
> >         } else {
> >                 dev_err(&rproc->dev, "Unrecognized option\n"); diff
> > --git a/drivers/remoteproc/remoteproc_sysfs.c
> > b/drivers/remoteproc/remoteproc_sysfs.c
> > index 51a04bc6ba7a..8c7ea8922638 100644
> > --- a/drivers/remoteproc/remoteproc_sysfs.c
> > +++ b/drivers/remoteproc/remoteproc_sysfs.c
> > @@ -194,23 +194,12 @@ static ssize_t state_store(struct device *dev,
> >         int ret = 0;
> >
> >         if (sysfs_streq(buf, "start")) {
> > -               if (rproc->state == RPROC_RUNNING ||
> > -                   rproc->state == RPROC_ATTACHED)
> > -                       return -EBUSY;
> > -
> 
> As per my previous comment the above conditions need to be moved into
> rproc_boot().
> 
> >                 ret = rproc_boot(rproc);
> >                 if (ret)
> >                         dev_err(&rproc->dev, "Boot failed: %d\n", ret);
> >         } else if (sysfs_streq(buf, "stop")) {
> > -               if (rproc->state != RPROC_RUNNING &&
> > -                   rproc->state != RPROC_ATTACHED)
> > -                       return -EINVAL;
> > -
> >                 ret = rproc_shutdown(rproc);
> >         } else if (sysfs_streq(buf, "detach")) {
> > -               if (rproc->state != RPROC_ATTACHED)
> > -                       return -EINVAL;
> > -
> 
> This patch should have been part of a patch series with your other work sent
> on March 18th[1].
> 
> Thanks,
> Mathieu
> 
> [1]. [PATCH] remoteproc: core: check rproc->power value before decreasing
> it
> 

Thanks for the comments.
I still have one question, if there are two instances independently to 'start'
'stop' remoteproc, for example:

Instance1: echo start > /sys/class/remoteproc/remoteproc0/state
Instance2: echo start > /sys/class/remoteproc/remoteproc0/state

...

Instance2: echo stop > /sys/class/remoteproc/remoteproc0/state
...
Instance1: echo stop > /sys/class/remoteproc/remoteproc0/state

When instance2 'stop' the remoteproc, then instance1 will be impacted for
It still needs the service from remoteproc.

That's why I just removed of the checking state, didn't move them to
rproc_boot()/rproc_shutdown()/rproc_detach(). And in order to utilize
the reference counter (rproc->power) to handle the multi-instance case.


Best regards
Wang Shengjiu