From: Petr Mladek <pmladek@suse.com> To: Vineet Gupta <vgupta@synopsys.com> Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>, Steven Rostedt <rostedt@goodmis.org>, John Ogness <john.ogness@linutronix.de>, Linus Torvalds <torvalds@linux-foundation.org>, Guenter Roeck <linux@roeck-us.net>, Shreyas Joshi <shreyas.joshi@biamp.com>, shreyasjoshi15@gmail.com, Greg Kroah-Hartman <gregkh@linuxfoundation.org>, Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>, linux-kernel@vger.kernel.org, buildroot@busybox.net, Thomas Petazzoni <thomas.petazzoni@bootlin.com>, linux-arch@vger.kernel.org, arcml <linux-snps-arc@lists.infradead.org> Subject: Re: ARC no console output (was Re: [PATCH 1/2] init/console: Use ttynull as a fallback when there is no console) Date: Thu, 7 Jan 2021 13:48:27 +0100 [thread overview] Message-ID: <X/cDG/xCCzSWW2cd@alley> (raw) In-Reply-To: <d2a3b3c0-e548-7dd1-730f-59bc5c04e191@synopsys.com> On Wed 2021-01-06 15:36:36, Vineet Gupta wrote: > +CC Buildroot folks > > Hi Petr, > > On 11/11/20 5:54 AM, Petr Mladek wrote: > > stdin, stdout, and stderr standard I/O stream are created for the init > > process. They are not available when there is no console registered > > for /dev/console. It might lead to a crash when the init process > > tries to use them, see the commit 48021f98130880dd742 ("printk: handle > > blank console arguments passed in."). > > > > Normally, ttySX and ttyX consoles are used as a fallback when no consoles > > are defined via the command line, device tree, or SPCR. But there > > will be no console registered when an invalid console name is configured > > or when the configured consoles do not exist on the system. > > > > Users even try to avoid the console intentionally, for example, > > by using console="" or console=null. It is used on production > > systems where the serial port or terminal are not visible to > > users. Pushing messages to these consoles would just unnecessary > > slowdown the system. > > > > Make sure that stdin, stdout, stderr, and /dev/console are always > > available by a fallback to the existing ttynull driver. It has > > been implemented for exactly this purpose but it was used only > > when explicitly configured. > > > > Signed-off-by: Petr Mladek <pmladek@suse.com> > > > --- a/init/main.c > > +++ b/init/main.c > > @@ -1470,8 +1470,14 @@ void __init console_on_rootfs(void) > > struct file *file = filp_open("/dev/console", O_RDWR, 0); > > if (IS_ERR(file)) { > > - pr_err("Warning: unable to open an initial console.\n"); > > - return; > > + pr_err("Warning: unable to open an initial console. Fallback to ttynull.\n"); > > + register_ttynull_console(); > > + > > + file = filp_open("/dev/console", O_RDWR, 0); > > + if (IS_ERR(file)) { > > + pr_err("Warning: Failed to add ttynull console. No stdin, stdout, and stderr for the init process!\n"); > > + return; > > + } > > > This breaks ARC booting (no output on console). This is likely the same problem as with kunit and um kernels. It is being discussed at https://lore.kernel.org/linux-kselftest/X%2FSRA1P8t+ONZFKb@alley/#t We have several workarounds. I am still squashing my head about the right solution. The console registration code is like a vasps' nest. It is always a pain when we touch it. I hope that I will send a patchset for review later today. In the worst case, we will revert the patch in the mainline. > Our Buildroot based setup has dynamic /dev where /dev/console doesn't exist > statically and there's a primoridla /init shell script which does following > > /bin/mount -t devtmpfs devtmpfs /dev > exec 0</dev/console > exec 1>/dev/console > exec 2>/dev/console > exec /sbin/init "$@" > > Buildroot has had this way of handling missing /dev/console since 2011 [1] > and [2]. Good to know. > Please advise what needs to be done to unbork boot. Otherwise this seems > like a kernel change which breaks user-space and needs to be backed-out (or > perhaps conditionalize on CONFIG_NULL_TTY. I'm surprised it hasn't been > reported by any other embedded folks Two workarounds can be fount at https://lore.kernel.org/linux-kselftest/X%2FSYhBZyudfnKY1u@alley/ https://lore.kernel.org/linux-kselftest/X%2FW2sl7RMvfaV4Ru@alley/ But I still see them as only a partial solutiuon. I still another sources of potential problems. Best Regards, Petr
WARNING: multiple messages have this Message-ID (diff)
From: Petr Mladek <pmladek@suse.com> To: Vineet Gupta <vgupta@synopsys.com> Cc: linux-arch@vger.kernel.org, Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>, John Ogness <john.ogness@linutronix.de>, Shreyas Joshi <shreyas.joshi@biamp.com>, linux-kernel@vger.kernel.org, Steven Rostedt <rostedt@goodmis.org>, Sergey Senozhatsky <sergey.senozhatsky@gmail.com>, Thomas Petazzoni <thomas.petazzoni@bootlin.com>, Greg Kroah-Hartman <gregkh@linuxfoundation.org>, buildroot@busybox.net, arcml <linux-snps-arc@lists.infradead.org>, Linus Torvalds <torvalds@linux-foundation.org>, shreyasjoshi15@gmail.com, Guenter Roeck <linux@roeck-us.net> Subject: Re: ARC no console output (was Re: [PATCH 1/2] init/console: Use ttynull as a fallback when there is no console) Date: Thu, 7 Jan 2021 13:48:27 +0100 [thread overview] Message-ID: <X/cDG/xCCzSWW2cd@alley> (raw) In-Reply-To: <d2a3b3c0-e548-7dd1-730f-59bc5c04e191@synopsys.com> On Wed 2021-01-06 15:36:36, Vineet Gupta wrote: > +CC Buildroot folks > > Hi Petr, > > On 11/11/20 5:54 AM, Petr Mladek wrote: > > stdin, stdout, and stderr standard I/O stream are created for the init > > process. They are not available when there is no console registered > > for /dev/console. It might lead to a crash when the init process > > tries to use them, see the commit 48021f98130880dd742 ("printk: handle > > blank console arguments passed in."). > > > > Normally, ttySX and ttyX consoles are used as a fallback when no consoles > > are defined via the command line, device tree, or SPCR. But there > > will be no console registered when an invalid console name is configured > > or when the configured consoles do not exist on the system. > > > > Users even try to avoid the console intentionally, for example, > > by using console="" or console=null. It is used on production > > systems where the serial port or terminal are not visible to > > users. Pushing messages to these consoles would just unnecessary > > slowdown the system. > > > > Make sure that stdin, stdout, stderr, and /dev/console are always > > available by a fallback to the existing ttynull driver. It has > > been implemented for exactly this purpose but it was used only > > when explicitly configured. > > > > Signed-off-by: Petr Mladek <pmladek@suse.com> > > > --- a/init/main.c > > +++ b/init/main.c > > @@ -1470,8 +1470,14 @@ void __init console_on_rootfs(void) > > struct file *file = filp_open("/dev/console", O_RDWR, 0); > > if (IS_ERR(file)) { > > - pr_err("Warning: unable to open an initial console.\n"); > > - return; > > + pr_err("Warning: unable to open an initial console. Fallback to ttynull.\n"); > > + register_ttynull_console(); > > + > > + file = filp_open("/dev/console", O_RDWR, 0); > > + if (IS_ERR(file)) { > > + pr_err("Warning: Failed to add ttynull console. No stdin, stdout, and stderr for the init process!\n"); > > + return; > > + } > > > This breaks ARC booting (no output on console). This is likely the same problem as with kunit and um kernels. It is being discussed at https://lore.kernel.org/linux-kselftest/X%2FSRA1P8t+ONZFKb@alley/#t We have several workarounds. I am still squashing my head about the right solution. The console registration code is like a vasps' nest. It is always a pain when we touch it. I hope that I will send a patchset for review later today. In the worst case, we will revert the patch in the mainline. > Our Buildroot based setup has dynamic /dev where /dev/console doesn't exist > statically and there's a primoridla /init shell script which does following > > /bin/mount -t devtmpfs devtmpfs /dev > exec 0</dev/console > exec 1>/dev/console > exec 2>/dev/console > exec /sbin/init "$@" > > Buildroot has had this way of handling missing /dev/console since 2011 [1] > and [2]. Good to know. > Please advise what needs to be done to unbork boot. Otherwise this seems > like a kernel change which breaks user-space and needs to be backed-out (or > perhaps conditionalize on CONFIG_NULL_TTY. I'm surprised it hasn't been > reported by any other embedded folks Two workarounds can be fount at https://lore.kernel.org/linux-kselftest/X%2FSYhBZyudfnKY1u@alley/ https://lore.kernel.org/linux-kselftest/X%2FW2sl7RMvfaV4Ru@alley/ But I still see them as only a partial solutiuon. I still another sources of potential problems. Best Regards, Petr _______________________________________________ linux-snps-arc mailing list linux-snps-arc@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-snps-arc
next prev parent reply other threads:[~2021-01-07 12:49 UTC|newest] Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-11-11 13:54 [PATCH 0/2] printk/console: Use ttynull when no console is available or wanted Petr Mladek 2020-11-11 13:54 ` [PATCH 1/2] init/console: Use ttynull as a fallback when there is no console Petr Mladek 2020-11-11 16:36 ` Greg Kroah-Hartman 2020-11-11 22:52 ` Guenter Roeck 2020-11-11 23:58 ` Sergey Senozhatsky 2020-11-12 0:17 ` Sergey Senozhatsky 2020-11-12 1:45 ` Sergey Senozhatsky 2020-11-16 16:20 ` Petr Mladek 2021-01-06 23:36 ` ARC no console output (was Re: [PATCH 1/2] init/console: Use ttynull as a fallback when there is no console) Vineet Gupta 2021-01-06 23:36 ` Vineet Gupta 2021-01-06 23:36 ` [Buildroot] " Vineet Gupta 2021-01-07 9:02 ` John Ogness 2021-01-07 9:02 ` John Ogness 2021-01-07 13:14 ` Greg Ungerer 2021-01-07 13:14 ` Greg Ungerer 2021-01-07 16:43 ` Vineet Gupta 2021-01-07 16:43 ` Vineet Gupta 2021-01-07 16:43 ` [Buildroot] " Vineet Gupta 2021-01-07 17:04 ` Petr Mladek 2021-01-07 17:04 ` Petr Mladek 2021-01-07 17:58 ` Vineet Gupta 2021-01-07 17:58 ` Vineet Gupta 2021-01-07 17:58 ` [Buildroot] " Vineet Gupta 2021-01-08 3:48 ` Sergey Senozhatsky 2021-01-08 3:48 ` Sergey Senozhatsky 2021-01-08 5:18 ` Vineet Gupta 2021-01-08 5:18 ` Vineet Gupta 2021-01-08 5:18 ` [Buildroot] " Vineet Gupta 2021-01-08 9:30 ` Petr Mladek 2021-01-08 9:30 ` Petr Mladek 2021-01-13 22:07 ` Peter Korsgaard 2021-01-13 22:07 ` Peter Korsgaard 2021-01-13 22:07 ` [Buildroot] " Peter Korsgaard 2021-01-07 9:09 ` Richard Weinberger 2021-01-07 9:09 ` Richard Weinberger 2021-01-07 12:48 ` Petr Mladek [this message] 2021-01-07 12:48 ` Petr Mladek 2021-01-07 15:27 ` [Buildroot] " Yann E. MORIN 2021-01-07 15:27 ` Yann E. MORIN 2021-01-07 15:27 ` Yann E. MORIN 2020-11-11 13:54 ` [PATCH 2/2] printk/console: Allow to disable console output by using console="" or console=null Petr Mladek 2020-11-11 22:52 ` Guenter Roeck 2020-11-11 23:59 ` Sergey Senozhatsky 2020-11-20 14:24 ` [PATCH 0/2] printk/console: Use ttynull when no console is available or wanted Petr Mladek
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