linux-kernel - [patch V2 01/13] USB: sisusbvga: Make console support depend on BROKEN

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Message-Id: <20201019101109.603244207@linutronix.de>
Date:   Mon, 19 Oct 2020 12:06:30 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Thomas Winischhofer <thomas@...ischhofer.net>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-usb@...r.kernel.org, stable@...r.kernel.org,
        "Ahmed S. Darwish" <a.darwish@...utronix.de>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Johan Hovold <johan@...nel.org>,
        Mathias Nyman <mathias.nyman@...el.com>,
        Valentina Manea <valentina.manea.m@...il.com>,
        Shuah Khan <shuah@...nel.org>,
        Alan Stern <stern@...land.harvard.edu>,
        linux-omap@...r.kernel.org, Kukjin Kim <kgene@...nel.org>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        linux-arm-kernel@...ts.infradead.org,
        linux-samsung-soc@...r.kernel.org, Felipe Balbi <balbi@...nel.org>,
        Duncan Sands <duncan.sands@...e.fr>
Subject: [patch V2 01/13] USB: sisusbvga: Make console support depend on BROKEN

The console part of sisusbvga is broken vs. printk(). It uses in_atomic()
to detect contexts in which it cannot sleep despite the big fat comment in
preempt.h which says: Do not use in_atomic() in driver code.

in_atomic() does not work on kernels with CONFIG_PREEMPT_COUNT=n which
means that spin/rw_lock held regions are not detected by it.

There is no way to make this work by handing context information through to
the driver and this only can be solved once the core printk infrastructure
supports sleepable console drivers.

Make it depend on BROKEN for now.

Fixes: 1bbb4f2035d9 ("[PATCH] USB: sisusb[vga] update")
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Cc: Thomas Winischhofer <thomas@...ischhofer.net>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: linux-usb@...r.kernel.org
Cc: stable@...r.kernel.org
---
 drivers/usb/misc/sisusbvga/Kconfig |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/usb/misc/sisusbvga/Kconfig
+++ b/drivers/usb/misc/sisusbvga/Kconfig
@@ -16,7 +16,7 @@ config USB_SISUSBVGA
 
 config USB_SISUSBVGA_CON
 	bool "Text console and mode switching support" if USB_SISUSBVGA
-	depends on VT
+	depends on VT && BROKEN
 	select FONT_8x16
 	help
 	  Say Y here if you want a VGA text console via the USB dongle or