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linux/arch/um/kernel
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Tejun Heo 196779b9b4 dump_stack: consolidate dump_stack() implementations and unify their behaviors 
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: Tejun Heo <tj@kernel.org>
Acked-by: David S. Miller <davem@davemloft.net>
Acked-by: Vineet Gupta <vgupta@synopsys.com>
Acked-by: Jesper Nilsson <jesper.nilsson@axis.com>
Acked-by: Vineet 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: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-04-30 17:04:02 -07:00
..
skas um: get rid of pointless include "..." where include <...> will do 2012-10-09 22:28:45 +02:00
asm-offsets.c um: get rid of pointless include "..." where include <...> will do 2012-10-09 22:28:45 +02:00
config.c.in um: get rid of pointless include "..." where include <...> will do 2012-10-09 22:28:45 +02:00
dyn.lds.S um: get rid of pointless include "..." where include <...> will do 2012-10-09 22:28:45 +02:00
early_printk.c early_printk: consolidate random copies of identical code 2013-04-29 18:28:13 -07:00
exec.c um: get_safe_registers() should be done in flush_thread(), not start_thread() 2012-11-28 21:46:03 -05:00
exitcode.c
gmon_syms.c um: get rid of pointless include "..." where include <...> will do 2012-10-09 22:28:45 +02:00
gprof_syms.c um: get rid of pointless include "..." where include <...> will do 2012-10-09 22:28:45 +02:00
initrd.c um: get rid of pointless include "..." where include <...> will do 2012-10-09 22:28:45 +02:00
irq.c um: get rid of pointless include "..." where include <...> will do 2012-10-09 22:28:45 +02:00
ksyms.c um: get rid of pointless include "..." where include <...> will do 2012-10-09 22:28:45 +02:00
Makefile um: Use generic init_task 2012-05-05 13:00:26 +02:00
mem.c mm/um: use free_highmem_page() to free highmem pages into buddy system 2013-04-29 15:54:32 -07:00
physmem.c um: distribute exports to where exported stuff is defined 2011-11-02 14:15:36 +01:00
process.c um: Use generic idle loop 2013-04-17 10:39:38 +02:00
ptrace.c um: split syscall_trace(), pass pt_regs to it 2012-08-02 00:25:38 +02:00
reboot.c um: get rid of pointless include "..." where include <...> will do 2012-10-09 22:28:45 +02:00
sigio.c um: get rid of pointless include "..." where include <...> will do 2012-10-09 22:28:45 +02:00
signal.c x86,um: switch to generic old sigsuspend() 2013-02-03 18:16:26 -05:00
smp.c um: get rid of pointless include "..." where include <...> will do 2012-10-09 22:28:45 +02:00
syscall.c x86, um: switch to generic fork/vfork/clone 2012-11-28 22:13:44 -05:00
sysrq.c dump_stack: consolidate dump_stack() implementations and unify their behaviors 2013-04-30 17:04:02 -07:00
time.c um: get rid of pointless include "..." where include <...> will do 2012-10-09 22:28:45 +02:00
tlb.c um: get rid of pointless include "..." where include <...> will do 2012-10-09 22:28:45 +02:00
trap.c Merge branch 'for-linus-37rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rw/uml 2012-10-10 11:15:20 +09:00
um_arch.c um: get rid of pointless include "..." where include <...> will do 2012-10-09 22:28:45 +02:00
umid.c um: get rid of pointless include "..." where include <...> will do 2012-10-09 22:28:45 +02:00
uml.lds.S um: get rid of pointless include "..." where include <...> will do 2012-10-09 22:28:45 +02:00
vmlinux.lds.S