Re: [PATCH v2 1/3] remoteproc: Fix unbalanced boot with sysfs for no auto-boot rprocs

[Mathieu Poirier]

On Fri, Nov 20, 2020 at 09:01:54PM -0600, Suman Anna wrote:
> The remoteproc core performs automatic boot and shutdown of a remote
> processor during rproc_add() and rproc_del() for remote processors
> supporting 'auto-boot'. The remoteproc devices not using 'auto-boot'
> require either a remoteproc client driver or a userspace client to
> use the sysfs 'state' variable to perform the boot and shutdown. The
> in-kernel client drivers hold the corresponding remoteproc driver
> module's reference count when they acquire a rproc handle through
> the rproc_get_by_phandle() API, but there is no such support for
> userspace applications performing the boot through sysfs interface.
> 
> The shutdown of a remoteproc upon removing a remoteproc platform
> driver is automatic only with 'auto-boot' and this can cause a
> remoteproc with no auto-boot to stay powered on and never freed
> up if booted using the sysfs interface without a matching stop,
> and when the remoteproc driver module is removed or unbound from
> the device. This will result in a memory leak as well as the
> corresponding remoteproc ida being never deallocated. Fix this
> by holding a module reference count for the remoteproc's driver
> during a sysfs 'start' and releasing it during the sysfs 'stop'
> operation.
> 
> Signed-off-by: Suman Anna <s-anna@xxxxxx>
> Acked-by: Arnaud Pouliquen <arnaud.pouliquen@xxxxxx>
> ---
> v2: rebased version, no changes
> v1: https://patchwork.kernel.org/project/linux-remoteproc/patch/20180915003725.17549-2-s-anna@xxxxxx/
> 
>  drivers/remoteproc/remoteproc_sysfs.c | 16 +++++++++++++++-
>  1 file changed, 15 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/remoteproc/remoteproc_sysfs.c b/drivers/remoteproc/remoteproc_sysfs.c
> index d1cf7bf277c4..bd2950a246c9 100644
> --- a/drivers/remoteproc/remoteproc_sysfs.c
> +++ b/drivers/remoteproc/remoteproc_sysfs.c
> @@ -3,6 +3,7 @@
>   * Remote Processor Framework
>   */
>  
> +#include <linux/module.h>
>  #include <linux/remoteproc.h>
>  #include <linux/slab.h>
>  
> @@ -228,14 +229,27 @@ static ssize_t state_store(struct device *dev,
>  		if (rproc->state == RPROC_RUNNING)
>  			return -EBUSY;
>  
> +		/*
> +		 * prevent underlying implementation from being removed
> +		 * when remoteproc does not support auto-boot
> +		 */
> +		if (!rproc->auto_boot &&
> +		    !try_module_get(dev->parent->driver->owner))
> +			return -EINVAL;
> +
>  		ret = rproc_boot(rproc);
> -		if (ret)
> +		if (ret) {
>  			dev_err(&rproc->dev, "Boot failed: %d\n", ret);
> +			if (!rproc->auto_boot)
> +				module_put(dev->parent->driver->owner);
> +		}
>  	} else if (sysfs_streq(buf, "stop")) {
>  		if (rproc->state != RPROC_RUNNING)
>  			return -EINVAL;
>  
>  		rproc_shutdown(rproc);
> +		if (!rproc->auto_boot)
> +			module_put(dev->parent->driver->owner);

I tackled the same problem by fixing another problem we had in the core.  Patch
2 [1] and 3 [2] of this set [3] get rid of the problem related to the auto_boot
check without having to deal with module counters.

Please see if that covers the use case you are dealing with.

Thanks,
Mathieu

[1]. https://patchwork.kernel.org/project/linux-remoteproc/patch/20201126210642.897302-3-mathieu.poirier@xxxxxxxxxx/
[2]. https://patchwork.kernel.org/project/linux-remoteproc/patch/20201126210642.897302-4-mathieu.poirier@xxxxxxxxxx/
[3]. https://patchwork.kernel.org/project/linux-remoteproc/list/?series=391789


>  	} else {
>  		dev_err(&rproc->dev, "Unrecognised option: %s\n", buf);
>  		ret = -EINVAL;
> -- 
> 2.28.0
>