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[65.112.8.24]) by smtp.gmail.com with ESMTPSA id af79cd13be357-820c974dbbbsm1145829885a.21.2025.09.17.07.57.24 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 17 Sep 2025 07:57:25 -0700 (PDT) Date: Wed, 17 Sep 2025 10:57:23 -0400 From: Alan Stern To: Hubert =?utf-8?Q?Wi=C5=9Bniewski?= Cc: Oleksij Rempel , Andrew Lunn , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Marek Szyprowski , stable@vger.kernel.org, kernel@pengutronix.de, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, Lukas Wunner , Russell King , Xu Yang , linux-usb@vger.kernel.org Subject: Re: [PATCH net v1 1/1] net: usb: asix: forbid runtime PM to avoid PM/MDIO + RTNL deadlock Message-ID: References: <20250917095457.2103318-1-o.rempel@pengutronix.de> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On Wed, Sep 17, 2025 at 04:31:40PM +0200, Hubert Wiśniewski wrote: > On Wed Sep 17, 2025 at 3:54 PM CEST, Alan Stern wrote: > > Are you aware that the action of pm_runtime_forbid() can be reversed by > > the user (by writing "auto" to the .../power/control sysfs file)? > > I have tested this. With this patch, it seems that writing "auto" to > power/control has no effect -- power/runtime_status remains "active" and > the device does not get suspended. But maybe there is a way to force the > suspension anyway? I don't know exactly what's going on in your particular case. However, if you read the source code for control_store() in drivers/base/power/sysfs.c, you'll see that writing "auto" to the attribute file causes the function to call pm_runtime_allow(). If you turn on CONFIG_PM_ADVANCED_DEBUG there will be extra files in the .../power/ directory, showing some of the other runtime PM values. Perhaps they will help you to figure out what's happening. Alan Stern