Re: [PATCH V4 3/9] nvme: fix race condition between connected uevent and STARTED_ONCE flag

[Hannes Reinecke <hare@suse.de>]

On 5/8/26 15:33, Maurizio Lombardi wrote:
> When a controller connects, nvme_start_ctrl() emits the
> "NVME_EVENT=connected" uevent and sets the NVME_CTRL_STARTED_ONCE flag.
> Currently, the uevent is emitted before the flag is set.
> 
> This creates a race condition for userspace tools (like udev rules)
> that might rely on the "connected" event to configure sysfs attributes.
> Specifically, if a udev rule attempts to set the newly introduced
> `admin_timeout` attribute immediately after receiving the uevent,
> the sysfs store function might evaluate the NVME_CTRL_STARTED_ONCE
> bit before it is actually set, resulting in spurious -EBUSY error.
> 
> Swap the order of operations in nvme_start_ctrl() so that the
> NVME_CTRL_STARTED_ONCE flag is set before the uevent is sent.
> This guarantees that the admin_timeout can already be changed
> when userspace is notified.
> 
> Signed-off-by: Maurizio Lombardi <mlombard@redhat.com>
> ---
>   drivers/nvme/host/core.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
> index b1bfcd0a0e5b..22be8cf5e982 100644
> --- a/drivers/nvme/host/core.c
> +++ b/drivers/nvme/host/core.c
> @@ -5039,8 +5039,8 @@ void nvme_start_ctrl(struct nvme_ctrl *ctrl)
>   		nvme_mpath_update(ctrl);
>   	}
>   
> -	nvme_change_uevent(ctrl, "NVME_EVENT=connected");
>   	set_bit(NVME_CTRL_STARTED_ONCE, &ctrl->flags);
> +	nvme_change_uevent(ctrl, "NVME_EVENT=connected");
>   }
>   EXPORT_SYMBOL_GPL(nvme_start_ctrl);
>   
Reviewed-by: Hannes Reinecke <hare@kernel.org>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                  Kernel Storage Architect
hare@suse.de                                +49 911 74053 688
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