Re: [PATCH] platform/x86/amd/hsmp: Use guard mutex to synchronize probe

["Ilpo Järvinen" <ilpo.jarvinen@linux.intel.com>]

On Wed, 25 Jun 2025, Suma Hegde wrote:

In the shortlog, drop word "guard". This should also mention ACPI as the 
legacy probe is not affected.

> When async probing is used, 2 hsmp_acpi_probe() calls can race and
> make a mess of things.

Too vague wording.

> So, add guard mutex to synchronize them.
>
> Suggested-by: Hans de Goede <hdegoede@redhat.com>
> Signed-off-by: Suma Hegde <suma.hegde@amd.com>
> Reviewed-by: Naveen Krishna Chatradhi <naveenkrishna.chatradhi@amd.com>
> ---
>  drivers/platform/x86/amd/hsmp/acpi.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/platform/x86/amd/hsmp/acpi.c b/drivers/platform/x86/amd/hsmp/acpi.c
> index 2f1faa82d13e..ab2b65f16d1d 100644
> --- a/drivers/platform/x86/amd/hsmp/acpi.c
> +++ b/drivers/platform/x86/amd/hsmp/acpi.c
> @@ -15,11 +15,13 @@
>  #include <linux/array_size.h>
>  #include <linux/bits.h>
>  #include <linux/bitfield.h>
> +#include <linux/cleanup.h>
>  #include <linux/device.h>
>  #include <linux/dev_printk.h>
>  #include <linux/ioport.h>
>  #include <linux/kstrtox.h>
>  #include <linux/module.h>
> +#include <linux/mutex.h>
>  #include <linux/platform_device.h>
>  #include <linux/sysfs.h>
>  #include <linux/uuid.h>
> @@ -44,6 +46,8 @@ struct hsmp_sys_attr {
>  	u32 msg_id;
>  };
>  
> +static DEFINE_MUTEX(hsmp_lock);
> +
>  static int amd_hsmp_acpi_rdwr(struct hsmp_socket *sock, u32 offset,
>  			      u32 *value, bool write)
>  {
> @@ -585,6 +589,8 @@ static int hsmp_acpi_probe(struct platform_device *pdev)
>  	if (!hsmp_pdev)
>  		return -ENOMEM;
>  
> +	guard(mutex)(&hsmp_lock);
> +
>  	if (!hsmp_pdev->is_probed) {
>  		hsmp_pdev->num_sockets = amd_num_nodes();
>  		if (hsmp_pdev->num_sockets == 0 || hsmp_pdev->num_sockets > MAX_AMD_NUM_NODES)

So is it just the ->sock alloc and misc dev registration that require
protection? (The latter doesn't even seem to require that if a local 
variable carries that information over.)

-- 
 i.