In (the unlikely) case our continuation merge buffer is busy, we unfortunately
can not merge further continuation printk()s into a single record and have to
store them separately, which leads to split-up output of these lines when they
are printed.

Add some flags about newlines and prefix existence to these records and try to
reconstruct the full line again, when the separated records are printed.
Reported-By: NMichael Neuling <mikey@neuling.org>
Cc: Dave Jones <davej@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Tested-By: NMichael Neuling <mikey@neuling.org>
Signed-off-by: NKay Sievers <kay@vrfy.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Restore support for partial reads of any size on /proc/kmsg, in case the
supplied read buffer is smaller than the record size.

Some people seem to think is is ia good idea to run:
  $ dd if=/proc/kmsg bs=1 of=...
as a klog bridge.

Resolves-bug: https://bugzilla.kernel.org/show_bug.cgi?id=44211Reported-by: NJukka Ollila <jiiksteri@gmail.com>
Signed-off-by: NKay Sievers <kay@vrfy.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

We suppress printing kmsg records to the console, which are already printed
immediately while we have received their fragments.

Newly registered boot consoles print the entire kmsg buffer during
registration. Clear the console-suppress flag after we skipped the record
during its first storage, so any later print will see these records as usual.
Signed-off-by: NKay Sievers <kay@vrfy.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

The /proc/kmsg read() interface is internally simply wired up to a sequence
of syslog() syscalls, which might are racy between their checks and actions,
regarding concurrency.

In the (very uncommon) case of concurrent readers of /dev/kmsg, relying on
usual O_NONBLOCK behavior, the recently introduced mutex might block an
O_NONBLOCK reader in read(), when poll() returns for it, but another process
has already read the data in the meantime. We've seen that while running
artificial test setups and tools that "fight" about /proc/kmsg data.

This restores the original /proc/kmsg behavior, where in case of concurrent
read()s, poll() might wake up but the read() syscall will just return 0 to
the caller, while another process has "stolen" the data.

This is in the general case not the expected behavior, but it is the exact
same one, that can easily be triggered with a 3.4 kernel, and some tools
might just rely on it.

The mutex is not needed, the original integrity issue which introduced it,
is in the meantime covered by:
  "fill buffer with more than a single message for SYSLOG_ACTION_READ"
  116e90b2

Cc: Yuanhan Liu <yuanhan.liu@linux.intel.com>
Acked-by: NJan Beulich <jbeulich@suse.com>
Signed-off-by: NKay Sievers <kay@vrfy.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

After the recent split of facility and level into separate variables,
we miss the facility value (always 0 for kernel-originated messages)
in the syslog prefix.

On Tue, Jul 3, 2012 at 12:45 PM, Dan Carpenter <dan.carpenter@oracle.com> wrote:
> Static checkers complain about the impossible condition here.
>
> In 084681d1 ('printk: flush continuation lines immediately to
> console'), we changed msg->level from being a u16 to being an unsigned
> 3 bit bitfield.

Cc: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: NKay Sievers <kay@vrfy.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Non-printable characters in the log data are hex-escaped to ensure safe
post processing. We need to escape a backslash we find in the data, to be
able to distinguish it from a backslash we add for the escaping.

Also escape the non-printable character 127.

Thanks to Miloslav Trmac for the heads up.
Reported-by: NMichael Neuling <mikey@neuling.org>
Signed-off-by: NKay Sievers <kay@vrfy.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

In function devkmsg_read/writev/llseek/poll/open()..., the function
raw_spin_lock/unlock is used, there is potential deadlock case happening.
CPU1: thread1 doing the cat /dev/kmsg:
        raw_spin_lock(&logbuf_lock);
        while (user->seq == log_next_seq) {
when thread1 run here, at this time one interrupt is coming on CPU1 and running
based on this thread,if the interrupt handle called the printk which need the
logbuf_lock spin also, it will cause deadlock.

So we should use raw_spin_lock/unlock_irq here.
Acked-by: NKay Sievers <kay@vrfy.org>
Signed-off-by: Nliu chuansheng <chuansheng.liu@intel.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Fix kernel-doc warnings in printk.c: use correct parameter name.

  Warning(kernel/printk.c:2429): No description found for parameter 'buf'
  Warning(kernel/printk.c:2429): Excess function parameter 'line' description in 'kmsg_dump_get_buffer'
Signed-off-by: NRandy Dunlap <rdunlap@xenotime.net>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

In reviewing Kay's fix up patch: "printk: Have printk() never buffer its
data", I found two if statements that could be combined and optimized.

Put together the two 'cont.len && cont.owner == current' if statements
into a single one, and check if we need to call cont_add(). This also
removes the unneeded double cont_flush() calls.

Link: http://lkml.kernel.org/r/1340869133.876.10.camel@mopSigned-off-by: NSteven Rostedt <rostedt@goodmis.org>
Cc: Kay Sievers <kay@vrfy.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Continuation lines are buffered internally, intended to merge the
chunked printk()s into a single record, and to isolate potentially
racy continuation users from usual terminated line users.

This though, has the effect that partial lines are not printed to
the console in the moment they are emitted. In case the kernel
crashes in the meantime, the potentially interesting printed
information would never reach the consoles.

Here we share the continuation buffer with the console copy logic,
and partial lines are always immediately flushed to the available
consoles. They are still buffered internally to improve the
readability and integrity of the messages and minimize the amount
of needed record headers to store.
Signed-off-by: NKay Sievers <kay@vrfy.org>
Tested-by: NSteven Rostedt <rostedt@goodmis.org>
Acked-by: NSteven Rostedt <rostedt@goodmis.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

The recent changes to the printk buffer management resulted in
SYSLOG_ACTION_READ to only return a single message, whereas previously
the buffer would get filled as much as possible. As, when too small to
fit everything, filling it to the last byte would be pretty ugly with
the new code, the patch arranges for as many messages as possible to
get returned in a single invocation. User space tools in at least all
SLES versions depend on the old behavior.

This at once addresses the issue attempted to get fixed with commit
b56a39ac ("printk: return -EINVAL if
the message len is bigger than the buf size"), and since that commit
widened the possibility for losing a message altogether, the patch
here assumes that this other commit would get reverted first
(otherwise the patch here won't apply).

Furthermore, this patch also addresses the problem dealt with in
commit 4a77a5a0 ("printk: use mutex
lock to stop syslog_seq from going wild"), so I'd recommend reverting
that one too (albeit there's no direct collision between the two).
Signed-off-by: NJan Beulich <jbeulich@suse.com>
Acked-by: NKay Sievers <kay@vrfy.org>
Cc: Yuanhan Liu <yuanhan.liu@linux.intel.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

This reverts commit b56a39ac.

A better patch from Jan will follow this to resolve the issue.
Acked-by: NKay Sievers <kay@vrfy.org>
Cc: Fengguang Wu <wfg@linux.intel.com>
Cc: Yuanhan Liu <yuanhan.liu@linux.intel.com>
Cc: Jan Beulich <JBeulich@suse.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Commit 7ff9554b (printk: convert
byte-buffer to variable-length record buffer) introduced a regression
by accidentally removing a "break" statement from inside the big
switch in printk's do_syslog().  The symptom of this bug is that the
"dmesg -C" command doesn't only clear the kernel's log buffer; it also
disables console logging.

This patch (as1561) fixes the regression by adding the missing
"break".
Signed-off-by: NAlan Stern <stern@rowland.harvard.edu>
CC: Kay Sievers <kay@vrfy.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Just like what devkmsg_read() does, return -EINVAL if the message len is
bigger than the buf size, or it will trigger a segfault error.
Acked-by: NKay Sievers <kay@vrfy.org>
Acked-by: NFengguang Wu <wfg@linux.intel.com>
Signed-off-by: NYuanhan Liu <yuanhan.liu@linux.intel.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Although syslog_seq and log_next_seq stuff are protected by logbuf_lock
spin log, it's not enough. Say we have two processes A and B, and let
syslog_seq = N, while log_next_seq = N + 1, and the two processes both
come to syslog_print at almost the same time. And No matter which
process get the spin lock first, it will increase syslog_seq by one,
then release spin lock; thus later, another process increase syslog_seq
by one again. In this case, syslog_seq is bigger than syslog_next_seq.
And latter, it would make:
   wait_event_interruptiable(log_wait, syslog != log_next_seq)
don't wait any more even there is no new write comes. Thus it introduce
a infinite loop reading.

I can easily see this kind of issue by the following steps:
  # cat /proc/kmsg # at meantime, I don't kill rsyslog
                   # So they are the two processes.
  # xinit          # I added drm.debug=6 in the kernel parameter line,
                   # so that it will produce lots of message and let that
                   # issue happen

It's 100% reproducable on my side. And my disk will be filled up by
/var/log/messages in a quite short time.

So, introduce a mutex_lock to stop syslog_seq from going wild just like
what devkmsg_read() does. It does fix this issue as expected.

v2: use mutex_lock_interruptiable() instead (comments from Kay)
Signed-off-by: NYuanhan Liu <yuanhan.liu@linux.intel.com>
Reviewed-by: NFengguang Wu <fengguang.wu@intel.com>
Acked-By: NKay Sievers <kay@vrfy.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Provide an iterator to receive the log buffer content, and convert all
kmsg_dump() users to it.

The structured data in the kmsg buffer now contains binary data, which
should no longer be copied verbatim to the kmsg_dump() users.

The iterator should provide reliable access to the buffer data, and also
supports proper log line-aware chunking of data while iterating.
Signed-off-by: NKay Sievers <kay@vrfy.org>
Tested-by: NTony Luck <tony.luck@intel.com>
Reported-by: NAnton Vorontsov <anton.vorontsov@linaro.org>
Tested-by: NAnton Vorontsov <anton.vorontsov@linaro.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Commit 7ff9554b, printk: convert
byte-buffer to variable-length record buffer, causes systems using
EABI to crash very early in the boot cycle. The first entry in struct
log is a u64, which for EABI must be 8 byte aligned.

Make use of __alignof__() so the compiler to decide the alignment, but
allow it to be overridden using CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS,
for systems which can perform unaligned access and want to save
a few bytes of space.

Tested on Orion5x and Kirkwood.
Signed-off-by: NAndrew Lunn <andrew@lunn.ch>
Tested-by: NStephen Warren <swarren@wwwdotorg.org>
Acked-by: NStephen Warren <swarren@wwwdotorg.org>
Acked-by: NKay Sievers <kay@vrfy.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Arrange the continuation printk() buffering to be fully separated from the
ordinary full line users.

Limit the exposure to races and wrong printk() line merges to users of
continuation only. Ordinary full line users racing against continuation
users will no longer affect each other.

Multiple continuation users from different threads, racing against each
other will not wrongly be merged into a single line, but printed as
separate lines.

Test output of a kernel module which starts two separate threads which
race against each other, one of them printing a single full terminated
line:
  printk("(AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA)\n");

The other one printing the line, every character separate in a
continuation loop:
  printk("(C");
  for (i = 0; i < 58; i++)
          printk(KERN_CONT "C");
  printk(KERN_CONT "C)\n");

Behavior of single and non-thread-aware printk() buffer:
  # modprobe printk-race
  printk test init
  (CC(AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA)
  C(AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA)
  CC(AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA)
  C(AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA)
  CC(AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA)
  C(AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA)
  C(AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA)
  CC(AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA)
  C(AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA)
  C(AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA)
  CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC)
  (CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC)

New behavior with separate and thread-aware continuation buffer:
  # modprobe printk-race
  printk test init
  (AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA)
  (AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA)
  (AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA)
  (CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC)
  (AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA)
  (AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA)
  (AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA)
  (AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA)
  (CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC)
  (CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC)

Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Joe Perches <joe@perches.com>
Cc: Ted Ts'o <tytso@mit.edu>
Cc: Ingo Molnar  <mingo@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Sasha Levin <levinsasha928@gmail.com>
Signed-off-by: NKay Sievers <kay@vrfy.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Calls like:
  printk("\n *** DEADLOCK ***\n\n");
will print 3 properly indented, separated, syslog + timestamp prefixed lines in
the log output.
Reported-By: NSasha Levin <levinsasha928@gmail.com>
Signed-off-by: NKay Sievers <kay@vrfy.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Add a stub for prepend_timestamp() when CONFIG_PRINTK is not
enabled.  Fixes this build error:

kernel/printk.c:1770:3: error: implicit declaration of function 'prepend_timestamp'

Cc: Kay Sievers <kay@vrfy.org>
Signed-off-by: NRandy Dunlap <rdunlap@xenotime.net>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

__log_buf must be aligned, because a 64-bit value is written directly
to it as part of struct log. Alignment of the log entries is typically
handled by log_store(), but this only triggers for subsequent entries,
not the very first (or wrapped) entries.

Cc: Kay Sievers <kay@vrfy.org>
Signed-off-by: NStephen Warren <swarren@nvidia.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

The output of the timestamps got lost with the conversion of the
kmsg buffer to records; restore the old behavior.

Document, that CONFIG_PRINTK_TIME now only controls the output of
the timestamps in the syslog() system call and on the console, and
not the recording of the timestamps.

Cc: Joe Perches <joe@perches.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Sasha Levin <levinsasha928@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Reported-by: NYinghai Lu <yinghai@kernel.org>
Signed-off-by: NKay Sievers <kay@vrfy.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

This prevents the merging of printk() continuation lines of different
threads, in the case they race against each other.

It should properly isolate "atomic" single-line printk() users from
continuation users, to make sure the single-line users will never be
merged with the racy continuation ones.

Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Sasha Levin <levinsasha928@gmail.com>
Signed-off-by: NKay Sievers <kay@vrfy.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Reported-by: NRandy Dunlap <rdunlap@xenotime.net>
Signed-off-by: NKay Sievers <kay@vrfy.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

On Tue, May 8, 2012 at 10:02 AM, Stephen Rothwell <sfr@canb.auug.org.au> wrote:
> kernel/built-in.o: In function `devkmsg_read':
> printk.c:(.text+0x27e8): undefined reference to `__udivdi3'
> Most probably the "msg->ts_nsec / 1000" since
> ts_nsec is a u64 and this is a 32 bit build ...
Reported-by: NStephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: NKay Sievers <kay@vrfy.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Support for multiple concurrent readers of /dev/kmsg, with read(),
seek(), poll() support. Output of message sequence numbers, to allow
userspace log consumers to reliably reconnect and reconstruct their
state at any given time. After open("/dev/kmsg"), read() always
returns *all* buffered records. If only future messages should be
read, SEEK_END can be used. In case records get overwritten while
/dev/kmsg is held open, or records get faster overwritten than they
are read, the next read() will return -EPIPE and the current reading
position gets updated to the next available record. The passed
sequence numbers allow the log consumer to calculate the amount of
lost messages.

  [root@mop ~]# cat /dev/kmsg
  5,0,0;Linux version 3.4.0-rc1+ (kay@mop) (gcc version 4.7.0 20120315 ...
  6,159,423091;ACPI: PCI Root Bridge [PCI0] (domain 0000 [bus 00-ff])
  7,160,424069;pci_root PNP0A03:00: host bridge window [io  0x0000-0x0cf7] (ignored)
   SUBSYSTEM=acpi
   DEVICE=+acpi:PNP0A03:00
  6,339,5140900;NET: Registered protocol family 10
  30,340,5690716;udevd[80]: starting version 181
  6,341,6081421;FDC 0 is a S82078B
  6,345,6154686;microcode: CPU0 sig=0x623, pf=0x0, revision=0x0
  7,346,6156968;sr 1:0:0:0: Attached scsi CD-ROM sr0
   SUBSYSTEM=scsi
   DEVICE=+scsi:1:0:0:0
  6,347,6289375;microcode: CPU1 sig=0x623, pf=0x0, revision=0x0

Cc: Karel Zak <kzak@redhat.com>
Tested-by: NWilliam Douglas <william.douglas@intel.com>
Signed-off-by: NKay Sievers <kay@vrfy.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

- Record-based stream instead of the traditional byte stream
  buffer. All records carry a 64 bit timestamp, the syslog facility
  and priority in the record header.

- Records consume almost the same amount, sometimes less memory than
  the traditional byte stream buffer (if printk_time is enabled). The record
  header is 16 bytes long, plus some padding bytes at the end if needed.
  The byte-stream buffer needed 3 chars for the syslog prefix, 15 char for
  the timestamp and a newline.

- Buffer management is based on message sequence numbers. When records
  need to be discarded, the reading heads move on to the next full
  record. Unlike the byte-stream buffer, no old logged lines get
  truncated or partly overwritten by new ones. Sequence numbers also
  allow consumers of the log stream to get notified if any message in
  the stream they are about to read gets discarded during the time
  of reading.

- Better buffered IO support for KERN_CONT continuation lines, when printk()
  is called multiple times for a single line. The use of KERN_CONT is now
  mandatory to use continuation; a few places in the kernel need trivial fixes
  here. The buffering could possibly be extended to per-cpu variables to allow
  better thread-safety for multiple printk() invocations for a single line.

- Full-featured syslog facility value support. Different facilities
  can tag their messages. All userspace-injected messages enforce a
  facility value > 0 now, to be able to reliably distinguish them from
  the kernel-generated messages. Independent subsystems like a
  baseband processor running its own firmware, or a kernel-related
  userspace process can use their own unique facility values. Multiple
  independent log streams can co-exist that way in the same
  buffer. All share the same global sequence number counter to ensure
  proper ordering (and interleaving) and to allow the consumers of the
  log to reliably correlate the events from different facilities.
Tested-by: NWilliam Douglas <william.douglas@intel.com>
Signed-off-by: NKay Sievers <kay@vrfy.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Commit 3ccf3e83 ("printk/sched: Introduce special
printk_sched() for those awkward moments") overlooked
an #ifdef, so move code around to respect these directives.
Reported-by: NStephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Randy Dunlap <rdunlap@xenotime.net>
Link: http://lkml.kernel.org/r/1331811337.18960.179.camel@twinsSigned-off-by: NIngo Molnar <mingo@elte.hu>

There's a few awkward printk()s inside of scheduler guts that people
prefer to keep but really are rather deadlock prone. Fudge around it
by storing the text in a per-cpu buffer and poll it using the existing
printk_tick() handler.

This will drop output when its more frequent than once a tick, however
only the affinity thing could possible go that fast and for that just
one should suffice to notify the admin he's done something silly..
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/n/tip-wua3lmkt3dg8nfts66o6brne@git.kernel.orgSigned-off-by: NIngo Molnar <mingo@elte.hu>

Since commit 04c6862c ("kmsg_dump: add kmsg_dump() calls to the
reboot, halt, poweroff and emergency_restart paths"), kmsg_dump() gets
run on normal paths including poweroff and reboot.

This is less than ideal given pstore implementations that can only
represent single backtraces, since a reboot may overwrite a stored oops
before it's been picked up by userspace.  In addition, some pstore
backends may have low performance and provide a significant delay in
reboot as a result.

This patch adds a printk.always_kmsg_dump kernel parameter (which can also
be changed from userspace).  Without it, the code will only be run on
failure paths rather than on normal paths.  The option can be enabled in
environments where there's a desire to attempt to audit whether or not a
reboot was cleanly requested or not.
Signed-off-by: NMatthew Garrett <mjg@redhat.com>
Acked-by: NSeiji Aguchi <seiji.aguchi@hds.com>
Cc: Seiji Aguchi <seiji.aguchi@hds.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Marco Stornelli <marco.stornelli@gmail.com>
Cc: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Don Zickus <dzickus@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Add a printk.console trace point to record any printk
messages into the trace, regardless of the current
console loglevel. This can help correlate (existing)
printk debugging with other tracing.

Link: http://lkml.kernel.org/r/1322161388.5366.54.camel@jlt3.sipsolutions.netAcked-by: NFrederic Weisbecker <fweisbec@gmail.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Ingo Molnar <mingo@redhat.com>
Acked-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: NThomas Gleixner <tglx@linutronix.de>
Signed-off-by: NJohannes Berg <johannes.berg@intel.com>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

module_param(bool) used to counter-intuitively take an int.  In
fddd5201 (mid-2009) we allowed bool or int/unsigned int using a messy
trick.

It's time to remove the int/unsigned int option.  For this version
it'll simply give a warning, but it'll break next kernel version.
Signed-off-by: NRusty Russell <rusty@rustcorp.com.au>

You don't need module_param_name if the name is the same!

Cc: Yanmin Zhang <yanmin_zhang@linux.intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: NRusty Russell <rusty@rustcorp.com.au>

Commit 4f2a8d3c ("printk: Fix console_sem vs logbuf_lock unlock race")
introduced another silly bug where we would want to acquire an already
held lock.  Avoid this.
Reported-by: NAndrea Arcangeli <aarcange@redhat.com>
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Switch to local_irq_ ops so that the irq state is properly tracked
(raw_local_irq_* isn't tracked by lockdep, causing confusion).

Possible now that commit dd4e5d3a ("lockdep: Fix
trace_[soft,hard]irqs_[on,off]() recursion") cured the reason we
needed the raw_ ops.
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

The raw_lock_irq_{save,restore}() already implies a
non-preemptibility.
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

zap_locks() is used by printk() in a last ditch effort to get data
out, clearly we cannot trust lock state after this so make it disable
lock debugging.

Also don't treat printk recursion through lockdep as a normal
recursion bug but try hard to get the lockdep splat out.
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/n/tip-kqxwmo4xz37e1s8w0xopvr0q@git.kernel.orgSigned-off-by: NIngo Molnar <mingo@elte.hu>

Currently log_prefix is testing that the first character of the log level
and facility is less than '0' and greater than '9' (which is always
false).

Since the code being updated works because strtoul bombs out (endp isn't
updated) and 0 is returned anyway just remove the check and don't change
the behavior of the function.
Signed-off-by: NWilliam Douglas <william.douglas@intel.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Currently log_prefix is testing that the first character of the log level
and facility is less than '0' and greater than '9' (which is always
false).  It should be testing to see if the character less than '0' or
greater than '9' instead.  This patch makes that change.

The code being changed worked because strtoul bombs out (endp isn't
updated) and 0 is returned anyway.
Signed-off-by: NWilliam Douglas <william.douglas@intel.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

We are enabling some power features on medfield.  To test suspend-2-RAM
conveniently, we need turn on/off console_suspend_enabled frequently.

Add a module parameter, so users could change it by:
/sys/module/printk/parameters/console_suspend
Signed-off-by: NYanmin Zhang <yanmin_zhang@linux.intel.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>