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  1. 13 12月, 2016 1 次提交
  3. 10 10月, 2016 1 次提交
    • L
      printk: reinstate KERN_CONT for printing continuation lines · 4bcc595c
      由 Linus Torvalds 提交于 
      Long long ago the kernel log buffer was a buffered stream of bytes, very
much like stdio in user space.  It supported log levels by scanning the
stream and noticing the log level markers at the beginning of each line,
but if you wanted to print a partial line in multiple chunks, you just
did multiple printk() calls, and it just automatically worked.

Except when it didn't, and you had very confusing output when different
lines got all mixed up with each other.  Then you got fragment lines
mixing with each other, or with non-fragment lines, because it was
traditionally impossible to tell whether a printk() call was a
continuation or not.

To at least help clarify the issue of continuation lines, we added a
KERN_CONT marker back in 2007 to mark continuation lines:

  47492527 ("printk: add KERN_CONT annotation").

That continuation marker was initially an empty string, and didn't
actuall make any semantic difference.  But it at least made it possible
to annotate the source code, and have check-patch notice that a printk()
didn't need or want a log level marker, because it was a continuation of
a previous line.

To avoid the ambiguity between a continuation line that had that
KERN_CONT marker, and a printk with no level information at all, we then
in 2009 made KERN_CONT be a real log level marker which meant that we
could now reliably tell the difference between the two cases.

  5fd29d6c ("printk: clean up handling of log-levels and newlines")

and we could take advantage of that to make sure we didn't mix up
continuation lines with lines that just didn't have any loglevel at all.

Then, in 2012, the kernel log buffer was changed to be a "record" based
log, where each line was a record that has a loglevel and a timestamp.

You can see the beginning of that conversion in commits

  e11fea92 ("kmsg: export printk records to the /dev/kmsg interface")
  7ff9554b ("printk: convert byte-buffer to variable-length record buffer")

with a number of follow-up commits to fix some painful fallout from that
conversion.  Over all, it took a couple of months to sort out most of
it.  But the upside was that you could have concurrent readers (and
writers) of the kernel log and not have lines with mixed output in them.

And one particular pain-point for the record-based kernel logging was
exactly the fragmentary lines that are generated in smaller chunks.  In
order to still log them as one recrod, the continuation lines need to be
attached to the previous record properly.

However the explicit continuation record marker that is actually useful
for this exact case was actually removed in aroundm the same time by commit

  61e99ab8 ("printk: remove the now unnecessary "C" annotation for KERN_CONT")

due to the incorrect belief that KERN_CONT wasn't meaningful.  The
ambiguity between "is this a continuation line" or "is this a plain
printk with no log level information" was reintroduced, and in fact
became an even bigger pain point because there was now the whole
record-level merging of kernel messages going on.

This patch reinstates the KERN_CONT as a real non-empty string marker,
so that the ambiguity is fixed once again.

But it's not a plain revert of that original removal: in the four years
since we made KERN_CONT an empty string again, not only has the format
of the log level markers changed, we've also had some usage changes in
this area.

For example, some ACPI code seems to use KERN_CONT _together_ with a log
level, and now uses both the KERN_CONT marker and (for example) a
KERN_INFO marker to show that it's an informational continuation of a
line.

Which is actually not a bad idea - if the continuation line cannot be
attached to its predecessor, without the log level information we don't
know what log level to assign to it (and we traditionally just assigned
it the default loglevel).  So having both a log level and the KERN_CONT
marker is not necessarily a bad idea, but it does mean that we need to
actually iterate over potentially multiple markers, rather than just a
single one.

Also, since KERN_CONT was still conceptually needed, and encouraged, but
didn't actually _do_ anything, we've also had the reverse problem:
rather than having too many annotations it has too few, and there is bit
rot with code that no longer marks the continuation lines with the
KERN_CONT marker.

So this patch not only re-instates the non-empty KERN_CONT marker, it
also fixes up the cases of bit-rot I noticed in my own logs.

There are probably other cases where KERN_CONT will be needed to be
added, either because it is new code that never dealt with the need for
KERN_CONT, or old code that has bitrotted without anybody noticing.

That said, we should strive to avoid the need for KERN_CONT.  It does
result in real problems for logging, and should generally not be seen as
a good feature.  If we some day can get rid of the feature entirely,
because nobody does any fragmented printk calls, that would be lovely.

But until that point, let's at mark the code that relies on the hacky
multi-fragment kernel printk's.  Not only does it avoid the ambiguity,
it also annotates code as "maybe this would be good to fix some day".

(That said, particularly during single-threaded bootup, the downsides of
KERN_CONT are very limited.  Things get much hairier when you have
multiple threads going on and user level reading and writing logs too).
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      4bcc595c
  5. 10 8月, 2016 1 次提交
    • L
      Revert "printk: create pr_<level> functions" · a0cba217
      由 Linus Torvalds 提交于 
      This reverts commit 874f9c7d.

Geert Uytterhoeven reports:
 "This change seems to have an (unintendent?) side-effect.

  Before, pr_*() calls without a trailing newline characters would be
  printed with a newline character appended, both on the console and in
  the output of the dmesg command.

  After this commit, no new line character is appended, and the output
  of the next pr_*() call of the same type may be appended, like in:

    - Truncating RAM at 0x0000000040000000-0x00000000c0000000 to -0x0000000070000000
    - Ignoring RAM at 0x0000000200000000-0x0000000240000000 (!CONFIG_HIGHMEM)
    + Truncating RAM at 0x0000000040000000-0x00000000c0000000 to -0x0000000070000000Ignoring RAM at 0x0000000200000000-0x0000000240000000 (!CONFIG_HIGHMEM)"

Joe Perches says:
 "No, that is not intentional.

  The newline handling code inside vprintk_emit is a bit involved and
  for now I suggest a revert until this has all the same behavior as
  earlier"
Reported-by: NGeert Uytterhoeven <geert@linux-m68k.org>
Requested-by: NJoe Perches <joe@perches.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      a0cba217
  7. 03 8月, 2016 3 次提交
  9. 08 7月, 2016 1 次提交
  11. 21 5月, 2016 2 次提交
    • P
      printk/nmi: flush NMI messages on the system panic · cf9b1106
      由 Petr Mladek 提交于 
      In NMI context, printk() messages are stored into per-CPU buffers to
avoid a possible deadlock.  They are normally flushed to the main ring
buffer via an IRQ work.  But the work is never called when the system
calls panic() in the very same NMI handler.

This patch tries to flush NMI buffers before the crash dump is
generated.  In this case it does not risk a double release and bails out
when the logbuf_lock is already taken.  The aim is to get the messages
into the main ring buffer when possible.  It makes them better
accessible in the vmcore.

Then the patch tries to flush the buffers second time when other CPUs
are down.  It might be more aggressive and reset logbuf_lock.  The aim
is to get the messages available for the consequent kmsg_dump() and
console_flush_on_panic() calls.

The patch causes vprintk_emit() to be called even in NMI context again.
But it is done via printk_deferred() so that the console handling is
skipped.  Consoles use internal locks and we could not prevent a
deadlock easily.  They are explicitly called later when the crash dump
is not generated, see console_flush_on_panic().
Signed-off-by: NPetr Mladek <pmladek@suse.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Daniel Thompson <daniel.thompson@linaro.org>
Cc: David Miller <davem@davemloft.net>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Jiri Kosina <jkosina@suse.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Russell King <rmk+kernel@arm.linux.org.uk>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      cf9b1106
    • P
      printk/nmi: generic solution for safe printk in NMI · 42a0bb3f
      由 Petr Mladek 提交于 
      printk() takes some locks and could not be used a safe way in NMI
context.

The chance of a deadlock is real especially when printing stacks from
all CPUs.  This particular problem has been addressed on x86 by the
commit a9edc880 ("x86/nmi: Perform a safe NMI stack trace on all
CPUs").

The patchset brings two big advantages.  First, it makes the NMI
backtraces safe on all architectures for free.  Second, it makes all NMI
messages almost safe on all architectures (the temporary buffer is
limited.  We still should keep the number of messages in NMI context at
minimum).

Note that there already are several messages printed in NMI context:
WARN_ON(in_nmi()), BUG_ON(in_nmi()), anything being printed out from MCE
handlers.  These are not easy to avoid.

This patch reuses most of the code and makes it generic.  It is useful
for all messages and architectures that support NMI.

The alternative printk_func is set when entering and is reseted when
leaving NMI context.  It queues IRQ work to copy the messages into the
main ring buffer in a safe context.

__printk_nmi_flush() copies all available messages and reset the buffer.
Then we could use a simple cmpxchg operations to get synchronized with
writers.  There is also used a spinlock to get synchronized with other
flushers.

We do not longer use seq_buf because it depends on external lock.  It
would be hard to make all supported operations safe for a lockless use.
It would be confusing and error prone to make only some operations safe.

The code is put into separate printk/nmi.c as suggested by Steven
Rostedt.  It needs a per-CPU buffer and is compiled only on
architectures that call nmi_enter().  This is achieved by the new
HAVE_NMI Kconfig flag.

The are MN10300 and Xtensa architectures.  We need to clean up NMI
handling there first.  Let's do it separately.

The patch is heavily based on the draft from Peter Zijlstra, see

  https://lkml.org/lkml/2015/6/10/327

[arnd@arndb.de: printk-nmi: use %zu format string for size_t]
[akpm@linux-foundation.org: min_t->min - all types are size_t here]
Signed-off-by: NPetr Mladek <pmladek@suse.com>
Suggested-by: NPeter Zijlstra <peterz@infradead.org>
Suggested-by: NSteven Rostedt <rostedt@goodmis.org>
Cc: Jan Kara <jack@suse.cz>
Acked-by: Russell King <rmk+kernel@arm.linux.org.uk>	[arm part]
Cc: Daniel Thompson <daniel.thompson@linaro.org>
Cc: Jiri Kosina <jkosina@suse.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: David Miller <davem@davemloft.net>
Cc: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      42a0bb3f
  13. 17 1月, 2016 1 次提交
  15. 11 9月, 2015 2 次提交
  17. 18 7月, 2015 1 次提交
    • N
      include, lib: add __printf attributes to several function prototypes · 8db14860
      由 Nicolas Iooss 提交于 
      Using __printf attributes helps to detect several format string issues
at compile time (even though -Wformat-security is currently disabled in
Makefile).  For example it can detect when formatting a pointer as a
number, like the issue fixed in commit a3fa71c4 ("wl18xx: show
rx_frames_per_rates as an array as it really is"), or when the arguments
do not match the format string, c.f.  for example commit 5ce1aca8
("reiserfs: fix __RASSERT format string").

To prevent similar bugs in the future, add a __printf attribute to every
function prototype which needs one in include/linux/ and lib/.  These
functions were mostly found by using gcc's -Wsuggest-attribute=format
flag.
Signed-off-by: NNicolas Iooss <nicolas.iooss_linux@m4x.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Felipe Balbi <balbi@ti.com>
Cc: Joel Becker <jlbec@evilplan.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      8db14860
  19. 26 6月, 2015 1 次提交
    • T
      printk: guard the amount written per line by devkmsg_read() · d43ff430
      由 Tejun Heo 提交于 
      This patchset updates netconsole so that it can emit messages with the
same header as used in /dev/kmsg which gives neconsole receiver full log
information which enables things like structured logging and detection
of lost messages.

This patch (of 7):

devkmsg_read() uses 8k buffer and assumes that the formatted output
message won't overrun which seems safe given LOG_LINE_MAX, the current use
of dict and the escaping method being used; however, we're planning to use
devkmsg formatting wider and accounting for the buffer size properly isn't
that complicated.

This patch defines CONSOLE_EXT_LOG_MAX as 8192 and updates devkmsg_read()
so that it limits output accordingly.
Signed-off-by: NTejun Heo <tj@kernel.org>
Cc: David Miller <davem@davemloft.net>
Cc: Kay Sievers <kay@vrfy.org>
Reviewed-by: NPetr Mladek <pmladek@suse.cz>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      d43ff430
  21. 16 4月, 2015 1 次提交
  23. 13 2月, 2015 1 次提交
  25. 27 1月, 2015 1 次提交
  27. 11 12月, 2014 1 次提交
  29. 22 11月, 2014 1 次提交
  31. 20 11月, 2014 1 次提交
  33. 13 8月, 2014 1 次提交
  35. 07 8月, 2014 1 次提交
    • A
      printk: rename DEFAULT_MESSAGE_LOGLEVEL · 42a9dc0b
      由 Alex Elder 提交于 
      Commit a8fe19eb ("kernel/printk: use symbolic defines for console
loglevels") makes consistent use of symbolic values for printk() log
levels.

The naming scheme used is different from the one used for
DEFAULT_MESSAGE_LOGLEVEL though.  Change that symbol name to be
MESSAGE_LOGLEVEL_DEFAULT for consistency.  And because the value of that
symbol comes from a similarly-named config option, rename
CONFIG_DEFAULT_MESSAGE_LOGLEVEL as well.
Signed-off-by: NAlex Elder <elder@linaro.org>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: Jan Kara <jack@suse.cz>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Petr Mladek <pmladek@suse.cz>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      42a9dc0b
  37. 05 6月, 2014 4 次提交
  39. 04 4月, 2014 2 次提交
  41. 24 1月, 2014 1 次提交
  43. 01 1月, 2014 1 次提交
  45. 30 10月, 2013 1 次提交
  47. 07 8月, 2013 1 次提交
  49. 22 5月, 2013 1 次提交
    • R
      Add include dependencies to <linux/printk.h>. · 154c2670
      由 Ralf Baechle 提交于 
      If <linux/linkage.h> has not been included before <linux/printk.h>,
a build error like the below one will result:

  CC      arch/mips/kernel/idle.o
In file included from arch/mips/kernel/idle.c:17:0:
include/linux/printk.h:109:1: error: data definition has no type or storage class [-Werror]
include/linux/printk.h:109:1: error: type defaults to ‘int’ in declaration of ‘asmlinkage’ [-Werror=implicit-int]
include/linux/printk.h:110:1: error: ‘format’ attribute only applies to function types [-Werror=attributes]
include/linux/printk.h:110:1: error: expected ‘,’ or ‘;’ before ‘int’
include/linux/printk.h:114:1: error: data definition has no type or storage class [-Werror]
include/linux/printk.h:114:1: error: type defaults to ‘int’ in declaration of ‘asmlinkage’ [-Werror=implicit-int]
include/linux/printk.h:115:1: error: ‘format’ attribute only applies to function types [-Werror=attributes]
include/linux/printk.h:115:1: error: expected ‘,’ or ‘;’ before ‘int’
include/linux/printk.h:117:1: error: data definition has no type or storage class [-Werror]
include/linux/printk.h:117:1: error: type defaults to ‘int’ in declaration of ‘asmlinkage’ [-Werror=implicit-int]
include/linux/printk.h:118:1: error: ‘format’ attribute only applies to function types [-Werror=attributes]
include/linux/printk.h:118:1: error: ‘__cold__’ attribute ignored [-Werror=attributes]
include/linux/printk.h:118:1: error: expected ‘,’ or ‘;’ before ‘asmlinkage’
include/linux/printk.h:122:1: error: data definition has no type or storage class [-Werror]
include/linux/printk.h:122:1: error: type defaults to ‘int’ in declaration of ‘asmlinkage’ [-Werror=implicit-int]
include/linux/printk.h:123:1: error: ‘format’ attribute only applies to function types [-Werror=attributes]
include/linux/printk.h:123:1: error: ‘__cold__’ attribute ignored [-Werror=attributes]
include/linux/printk.h:123:1: error: expected ‘,’ or ‘;’ before ‘int’
In file included from include/linux/kernel.h:14:0,
                 from include/linux/sched.h:15,
                 from arch/mips/kernel/idle.c:18:
include/linux/dynamic_debug.h: In function ‘ddebug_dyndbg_module_param_cb’:
include/linux/dynamic_debug.h:124:3: error: implicit declaration of function ‘printk’ [-Werror=implicit-function-declaration]

Fixed by including <linux/linkage.h>.
Signed-off-by: NRalf Baechle <ralf@linux-mips.org>
      154c2670
  51. 01 5月, 2013 3 次提交
    • T
      dump_stack: unify debug information printed by show_regs() · a43cb95d
      由 Tejun Heo 提交于 
      show_regs() is inherently arch-dependent but it does make sense to print
generic debug information and some archs already do albeit in slightly
different forms.  This patch introduces a generic function to print debug
information from show_regs() so that different archs print out the same
information and it's much easier to modify what's printed.

show_regs_print_info() prints out the same debug info as dump_stack()
does plus task and thread_info pointers.

* Archs which didn't print debug info now do.

  alpha, arc, blackfin, c6x, cris, frv, h8300, hexagon, ia64, m32r,
  metag, microblaze, mn10300, openrisc, parisc, score, sh64, sparc,
  um, xtensa

* Already prints debug info.  Replaced with show_regs_print_info().
  The printed information is superset of what used to be there.

  arm, arm64, avr32, mips, powerpc, sh32, tile, unicore32, x86

* s390 is special in that it used to print arch-specific information
  along with generic debug info.  Heiko and Martin think that the
  arch-specific extra isn't worth keeping s390 specfic implementation.
  Converted to use the generic version.

Note that now all archs print the debug info before actual register
dumps.

An example BUG() dump follows.

 kernel BUG at /work/os/work/kernel/workqueue.c:4841!
 invalid opcode: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC
 Modules linked in:
 CPU: 0 PID: 1 Comm: swapper/0 Not tainted 3.9.0-rc1-work+ #7
 Hardware name: empty empty/S3992, BIOS 080011  10/26/2007
 task: ffff88007c85e040 ti: ffff88007c860000 task.ti: ffff88007c860000
 RIP: 0010:[<ffffffff8234a07e>]  [<ffffffff8234a07e>] init_workqueues+0x4/0x6
 RSP: 0000:ffff88007c861ec8  EFLAGS: 00010246
 RAX: ffff88007c861fd8 RBX: ffffffff824466a8 RCX: 0000000000000001
 RDX: 0000000000000046 RSI: 0000000000000001 RDI: ffffffff8234a07a
 RBP: ffff88007c861ec8 R08: 0000000000000000 R09: 0000000000000000
 R10: 0000000000000001 R11: 0000000000000000 R12: ffffffff8234a07a
 R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
 FS:  0000000000000000(0000) GS:ffff88007dc00000(0000) knlGS:0000000000000000
 CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
 CR2: ffff88015f7ff000 CR3: 00000000021f1000 CR4: 00000000000007f0
 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
 DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
 Stack:
  ffff88007c861ef8 ffffffff81000312 ffffffff824466a8 ffff88007c85e650
  0000000000000003 0000000000000000 ffff88007c861f38 ffffffff82335e5d
  ffff88007c862080 ffffffff8223d8c0 ffff88007c862080 ffffffff81c47760
 Call Trace:
  [<ffffffff81000312>] do_one_initcall+0x122/0x170
  [<ffffffff82335e5d>] kernel_init_freeable+0x9b/0x1c8
  [<ffffffff81c47760>] ? rest_init+0x140/0x140
  [<ffffffff81c4776e>] kernel_init+0xe/0xf0
  [<ffffffff81c6be9c>] ret_from_fork+0x7c/0xb0
  [<ffffffff81c47760>] ? rest_init+0x140/0x140
  ...

v2: Typo fix in x86-32.

v3: CPU number dropped from show_regs_print_info() as
    dump_stack_print_info() has been updated to print it.  s390
    specific implementation dropped as requested by s390 maintainers.
Signed-off-by: NTejun Heo <tj@kernel.org>
Acked-by: NDavid S. Miller <davem@davemloft.net>
Acked-by: NJesper Nilsson <jesper.nilsson@axis.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Fengguang Wu <fengguang.wu@intel.com>
Cc: Mike Frysinger <vapier@gentoo.org>
Cc: Vineet Gupta <vgupta@synopsys.com>
Cc: Sam Ravnborg <sam@ravnborg.org>
Acked-by: Chris Metcalf <cmetcalf@tilera.com>		[tile bits]
Acked-by: Richard Kuo <rkuo@codeaurora.org>		[hexagon bits]
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      a43cb95d
    • T
      dump_stack: implement arch-specific hardware description in task dumps · 98e5e1bf
      由 Tejun Heo 提交于 
      x86 and ia64 can acquire extra hardware identification information
from DMI and print it along with task dumps; however, the usage isn't
consistent.

* x86 show_regs() collects vendor, product and board strings and print
  them out with PID, comm and utsname.  Some of the information is
  printed again later in the same dump.

* warn_slowpath_common() explicitly accesses the DMI board and prints
  it out with "Hardware name:" label.  This applies to both x86 and
  ia64 but is irrelevant on all other archs.

* ia64 doesn't show DMI information on other non-WARN dumps.

This patch introduces arch-specific hardware description used by
dump_stack().  It can be set by calling dump_stack_set_arch_desc()
during boot and, if exists, printed out in a separate line with
"Hardware name:" label.

dmi_set_dump_stack_arch_desc() is added which sets arch-specific
description from DMI data.  It uses dmi_ids_string[] which is set from
dmi_present() used for DMI debug message.  It is superset of the
information x86 show_regs() is using.  The function is called from x86
and ia64 boot code right after dmi_scan_machine().

This makes the explicit DMI handling in warn_slowpath_common()
unnecessary.  Removed.

show_regs() isn't yet converted to use generic debug information
printing and this patch doesn't remove the duplicate DMI handling in
x86 show_regs().  The next patch will unify show_regs() handling and
remove the duplication.

An example WARN dump follows.

 WARNING: at kernel/workqueue.c:4841 init_workqueues+0x35/0x505()
 Modules linked in:
 CPU: 0 PID: 1 Comm: swapper/0 Not tainted 3.9.0-rc1-work+ #3
 Hardware name: empty empty/S3992, BIOS 080011  10/26/2007
  0000000000000009 ffff88007c861e08 ffffffff81c614dc ffff88007c861e48
  ffffffff8108f500 ffffffff82228240 0000000000000040 ffffffff8234a08e
  0000000000000000 0000000000000000 0000000000000000 ffff88007c861e58
 Call Trace:
  [<ffffffff81c614dc>] dump_stack+0x19/0x1b
  [<ffffffff8108f500>] warn_slowpath_common+0x70/0xa0
  [<ffffffff8108f54a>] warn_slowpath_null+0x1a/0x20
  [<ffffffff8234a0c3>] init_workqueues+0x35/0x505
  ...

v2: Use the same string as the debug message from dmi_present() which
    also contains BIOS information.  Move hardware name into its own
    line as warn_slowpath_common() did.  This change was suggested by
    Bjorn Helgaas.
Signed-off-by: NTejun Heo <tj@kernel.org>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Fengguang Wu <fengguang.wu@intel.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Jesper Nilsson <jesper.nilsson@axis.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Mike Frysinger <vapier@gentoo.org>
Cc: Vineet Gupta <vgupta@synopsys.com>
Cc: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      98e5e1bf
    • T
      dump_stack: consolidate dump_stack() implementations and unify their behaviors · 196779b9
      由 Tejun Heo 提交于 
      Both dump_stack() and show_stack() are currently implemented by each
architecture.  show_stack(NULL, NULL) dumps the backtrace for the
current task as does dump_stack().  On some archs, dump_stack() prints
extra information - pid, utsname and so on - in addition to the
backtrace while the two are identical on other archs.

The usages in arch-independent code of the two functions indicate
show_stack(NULL, NULL) should print out bare backtrace while
dump_stack() is used for debugging purposes when something went wrong,
so it does make sense to print additional information on the task which
triggered dump_stack().

There's no reason to require archs to implement two separate but mostly
identical functions.  It leads to unnecessary subtle information.

This patch expands the dummy fallback dump_stack() implementation in
lib/dump_stack.c such that it prints out debug information (taken from
x86) and invokes show_stack(NULL, NULL) and drops arch-specific
dump_stack() implementations in all archs except blackfin.  Blackfin's
dump_stack() does something wonky that I don't understand.

Debug information can be printed separately by calling
dump_stack_print_info() so that arch-specific dump_stack()
implementation can still emit the same debug information.  This is used
in blackfin.

This patch brings the following behavior changes.

* On some archs, an extra level in backtrace for show_stack() could be
  printed.  This is because the top frame was determined in
  dump_stack() on those archs while generic dump_stack() can't do that
  reliably.  It can be compensated by inlining dump_stack() but not
  sure whether that'd be necessary.

* Most archs didn't use to print debug info on dump_stack().  They do
  now.

An example WARN dump follows.

 WARNING: at kernel/workqueue.c:4841 init_workqueues+0x35/0x505()
 Hardware name: empty
 Modules linked in:
 CPU: 0 PID: 1 Comm: swapper/0 Not tainted 3.9.0-rc1-work+ #9
  0000000000000009 ffff88007c861e08 ffffffff81c614dc ffff88007c861e48
  ffffffff8108f50f ffffffff82228240 0000000000000040 ffffffff8234a03c
  0000000000000000 0000000000000000 0000000000000000 ffff88007c861e58
 Call Trace:
  [<ffffffff81c614dc>] dump_stack+0x19/0x1b
  [<ffffffff8108f50f>] warn_slowpath_common+0x7f/0xc0
  [<ffffffff8108f56a>] warn_slowpath_null+0x1a/0x20
  [<ffffffff8234a071>] init_workqueues+0x35/0x505
  ...

v2: CPU number added to the generic debug info as requested by s390
    folks and dropped the s390 specific dump_stack().  This loses %ksp
    from the debug message which the maintainers think isn't important
    enough to keep the s390-specific dump_stack() implementation.

    dump_stack_print_info() is moved to kernel/printk.c from
    lib/dump_stack.c.  Because linkage is per objecct file,
    dump_stack_print_info() living in the same lib file as generic
    dump_stack() means that archs which implement custom dump_stack()
    - at this point, only blackfin - can't use dump_stack_print_info()
    as that will bring in the generic version of dump_stack() too.  v1
    The v1 patch broke build on blackfin due to this issue.  The build
    breakage was reported by Fengguang Wu.
Signed-off-by: NTejun Heo <tj@kernel.org>
Acked-by: NDavid S. Miller <davem@davemloft.net>
Acked-by: NVineet Gupta <vgupta@synopsys.com>
Acked-by: NJesper Nilsson <jesper.nilsson@axis.com>
Acked-by: NVineet Gupta <vgupta@synopsys.com>
Acked-by: Martin Schwidefsky <schwidefsky@de.ibm.com>	[s390 bits]
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Mike Frysinger <vapier@gentoo.org>
Cc: Fengguang Wu <fengguang.wu@intel.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Sam Ravnborg <sam@ravnborg.org>
Acked-by: Richard Kuo <rkuo@codeaurora.org>		[hexagon bits]
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      196779b9
  53. 30 4月, 2013 2 次提交
  55. 23 3月, 2013 1 次提交
    • F
      printk: Provide a wake_up_klogd() off-case · dc72c32e
      由 Frederic Weisbecker 提交于 
      wake_up_klogd() is useless when CONFIG_PRINTK=n because neither printk()
nor printk_sched() are in use and there are actually no waiter on
log_wait waitqueue.  It should be a stub in this case for users like
bust_spinlocks().

Otherwise this results in this warning when CONFIG_PRINTK=n and
CONFIG_IRQ_WORK=n:

	kernel/built-in.o In function `wake_up_klogd':
	(.text.wake_up_klogd+0xb4): undefined reference to `irq_work_queue'

To fix this, provide an off-case for wake_up_klogd() when
CONFIG_PRINTK=n.

There is much more from console_unlock() and other console related code
in printk.c that should be moved under CONFIG_PRINTK.  But for now,
focus on a minimal fix as we passed the merged window already.

[akpm@linux-foundation.org: include printk.h in bust_spinlocks.c]
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>
Reported-by: NJames Hogan <james.hogan@imgtec.com>
Cc: James Hogan <james.hogan@imgtec.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      dc72c32e
  57. 22 2月, 2013 1 次提交