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a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1602688729; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: references:references; bh=j+vN9MgqREoIPGzBU7B1IaC3gna3kE7EN539Nh0ClUU=; b=OrT6mgTchqOnwodWRSOWnTUctuEN6qg/WU3nIlLDVaCTruOVTQIY5kwbMcQtZllOQS8XNQ DAfGWB0ldz/F46CA== Date: Wed, 14 Oct 2020 16:52:17 +0200 From: Thomas Gleixner To: LKML Subject: [patch 02/12] USB: serial: keyspan_pda: Replace in_interrupt() usage References: <20201014145215.518912759@linutronix.de> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20201014_111850_400921_F845A74C X-CRM114-Status: GOOD ( 17.18 ) X-Spam-Score: -2.5 (--) X-Spam-Report: SpamAssassin version 3.4.4 on merlin.infradead.org summary: Content analysis details: (-2.5 points) pts rule name description ---- ---------------------- -------------------------------------------------- -2.3 RCVD_IN_DNSWL_MED RBL: Sender listed at https://www.dnswl.org/, medium trust [193.142.43.55 listed in list.dnswl.org] 0.0 SPF_HELO_NONE SPF: HELO does not publish an SPF Record -0.0 SPF_PASS SPF: sender matches SPF record -0.1 DKIM_VALID_AU Message has a valid DKIM or DK signature from author's domain -0.1 DKIM_VALID_EF Message has a valid DKIM or DK signature from envelope-from domain -0.1 DKIM_VALID Message has at least one valid DKIM or DK signature 0.1 DKIM_SIGNED Message has a DKIM or DK signature, not necessarily valid X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Felipe Balbi , Thomas Winischhofer , Mathias Nyman , Peter Zijlstra , Greg Kroah-Hartman , Sebastian Andrzej Siewior , linux-usb@vger.kernel.org, Johan Hovold , Krzysztof Kozlowski , Valentina Manea , linux-samsung-soc@vger.kernel.org, Kukjin Kim , Alan Stern , Duncan Sands , "Ahmed S. Darwish" , linux-omap@vger.kernel.org, Shuah Khan , linux-arm-kernel@lists.infradead.org Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org keyspan_pda_write() uses in_interrupt() to check whether it is safe to invoke functions which might sleep. The usage of in_interrupt() in drivers is phased out and Linus clearly requested that code which changes behaviour depending on context should either be seperated or the context be conveyed in an argument passed by the caller, which usually knows the context. Aside of that it does not cover all contexts which cannot sleep, e.g. preempt disabled regions which cannot be reliably detected on all kernel configurations. With the current printk() implementation console->write() can be invoked from almost any context. The upcoming rework of the console core will provide thread context for console drivers which require to sleep. For now, restrict the room query which can sleep to tty writes which happen from preemptible task context. The usability for dmesg output is limited anyway because it's almost guaranteed to drop the 'LF' which is submitted after the dmesg line because the device supports only one transfer on flight. Same for any printk() which is coming in before the previous transfer has been done. This new restriction does not make it worse than before, but it makes the condition correct under all circumstances. Signed-off-by: Ahmed S. Darwish Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Thomas Gleixner Cc: Johan Hovold Cc: Greg Kroah-Hartman Cc: linux-usb@vger.kernel.org --- drivers/usb/serial/keyspan_pda.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) --- a/drivers/usb/serial/keyspan_pda.c +++ b/drivers/usb/serial/keyspan_pda.c @@ -477,10 +477,12 @@ static int keyspan_pda_write(struct tty_ count = (count > port->bulk_out_size) ? port->bulk_out_size : count; - /* Check if we might overrun the Tx buffer. If so, ask the - device how much room it really has. This is done only on - scheduler time, since usb_control_msg() sleeps. */ - if (count > priv->tx_room && !in_interrupt()) { + /* + * Check if we might overrun the Tx buffer. If so, ask the device + * how much room it really has. This can only be invoked for tty + * usage because the console write can't sleep. + */ + if (count > priv->tx_room && tty) { u8 *room; room = kmalloc(1, GFP_KERNEL);