Currently printk is no use for early debugging because it refuses to
actually print anything to the console unless
cpu_online(smp_processor_id()) is true.

The stated explanation is that console drivers may require per-cpu
resources, or otherwise barf, because the system is not yet setup
correctly.  Fair enough.

However some console drivers might be quite happy running early during
boot, in fact we have one, and so it'd be nice if printk understood that.

So I added a flag (which I would have called CON_BOOT, but that's taken)
called CON_ANYTIME, which indicates that a console is happy to be called
anytime, even if the cpu is not yet online.

Tested on a Power 5 machine, with both a CON_ANYTIME driver and a bogus
console driver that BUG()s if called while offline.  No problems AFAICT.
Built for i386 UP & SMP.
Signed-off-by: NMichael Ellerman <michael@ellerman.id.au>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Trying to suspend/resume with console messages flying all around is
doomed to failure, when the devices that the messages are trying to
go to are being shut down.
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

this changes if() BUG(); constructs to BUG_ON() which is
cleaner, contains unlikely() and can better optimized away.
Signed-off-by: NEric Sesterhenn <snakebyte@gmx.de>
Signed-off-by: NAdrian Bunk <bunk@stusta.de>

It appears that console_setup() code only gets compiled into the kernel if
CONFIG_PRINTK is enabled.  One detrimental side-effect of this is that
serial8250_console_setup() never gets invoked when CONFIG_PRINTK is not
set, resulting in baud rate not being read/parsed from command line (i.e.
console=ttyS0,115200n8 is ignored, at least the baud rate part...)

Attached patch moves console_setup() code from inside

#ifdef CONFIG_PRINTK

to outside (in printk.c), removing dependence on said config. option.
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

I  tried to send the forcedeth maintainer an email, but it came back with:

"The mail address manfreds@colorfullife.com is not read anymore.
Please resent your mail to manfred@ instead of manfreds@."

This patch fixes this.
Signed-off-by: NAdrian Bunk <bunk@stusta.de>

What's the true meaning of the printk return value?  Should it include the
priority prefix length of 3?  and what about the timing information?  In
both cases it was broken:

strace -e write echo 1 > /dev/kmsg
=> write(1, "1\n", 2)                      = 5
strace -e write echo "<1>1" > /dev/kmsg
=> write(1, "<1>1\n", 5)                   = 8

The returned length was "length of input string + 3", I made it "length
of string output to the log buffer".

Note that I couldn't find any printk caller in the kernel interested by its
return value besides kmsg_write.
Signed-off-by: NGuillaume Chazarain <guichaz@yahoo.fr>
Acked-By: NTim Bird <tim.bird@am.sony.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

If unregister_console() is inadvertently called while no consoles are
registered, it will crash trying to dereference NULL pointer.  It is
necessary to fix that because register_console() provides no indication
that it actually registered the console passed in.  In fact, it may well
decide not to register it based on various things...

(akpm: It'd be better to make register_console() return something and fix the
callers.  All 106 of them...)
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Add printk documentation to kernel-api.
Signed-off-by: NMartin Waitz <tali@admingilde.org>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

I didn't find any possible modular usage of console_unblank in the
kernel.

This patch was already ACK'ed by Alan Cox.
Signed-off-by: NAdrian Bunk <bunk@stusta.de>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

- Removes some trailing whitespace

- Breaks long lines and make other small changes to conform to CodingStyle

- Add explicit printk loglevels in two places.
Signed-off-by: NJesper Juhl <jesper.juhl@gmail.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

ia64's sched_clock() accesses per-cpu data which isn't set up at boot time.
Hence ia64 cannot use printk timestamping, because printk() will crash in
sched_clock().

So make printk() use printk_clock(), defaulting to sched_clock(), overrideable
by the architecture via attribute(weak).

Cc: "Luck, Tony" <tony.luck@intel.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

The attached patch prevents oopses interleaving with characters from
other printks on other CPUs by only breaking the lock if the oops is
happening on the machine holding the lock.

It might be better if the oops generator got the lock and then called an
inner vprintk routine that assumed the caller holds the lock, thus
making oops reports "atomic".
Signed-Off-By: NDavid Howells <dhowells@redhat.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

In the cpu hotplug case, per-cpu data possibly isn't initialized even the
system state is 'running'.  As the comments say in the original code, some
console drivers assume per-cpu resources have been allocated.  radeon fb is
one such driver, which uses kmalloc.  After a CPU is down, the per-cpu data
of slab is freed, so the system crashed when printing some info.
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

According to include/linux/console.h, CON_CONSDEV flag should be set on
the last console specified on the boot command line:

     86 #define CON_PRINTBUFFER (1)
     87 #define CON_CONSDEV     (2) /* Last on the command line */
     88 #define CON_ENABLED     (4)
     89 #define CON_BOOT        (8)

This does not currently happen if there is more than one console specified
on the boot commandline.  Instead, it gets set on the first console on the
command line.  This can cause problems for things like kdb that look for
the CON_CONSDEV flag to see if the console is valid.

Additionaly, it doesn't look like CON_CONSDEV is reassigned to the next
preferred console at unregister time if the console being unregistered
currently has that bit set.

Example (from sn2 ia64):

elilo vmlinuz root=<dev> console=ttyS0 console=ttySG0

in this case, the flags on ttySG console struct will be 0x4 (should be
0x6).

Attached patch against bk fixes both issues for the cases I looked at.  It
uses selected_console (which gets incremented for each console specified on
the command line) as the indicator of which console to set CON_CONSDEV on.
When adding the console to the list, if the previous one had CON_CONSDEV
set, it masks it out.  Tested on ia64 and x86.

The problem with the current behavior is it breaks overriding the default from
the boot line.  In the ia64 case, there may be a global append line defining
console=a in elilo.conf.  Then you want to boot your kernel, and want to
override the default by passing console=b on the boot line.  elilo constructs
the kernel cmdline by starting with the value of the global append line, then
tacks on whatever else you specify, which puts console=b last.
Signed-off-by: NGreg Edwards <edwardsg@sgi.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Move add_preferred_console out of CONFIG_PRINTK so serial console does the
right thing.
Signed-off-by: NMatt Mackall <mpm@selenic.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Arrange for all kernel printks to be no-ops.  Only available if
CONFIG_EMBEDDED.

This patch saves about 375k on my laptop config and nearly 100k on minimal
configs.
Signed-off-by: NMatt Mackall <mpm@selenic.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.

Let it rip!