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+ hardkernel#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 <[email protected]>
Acked-by: David S. Miller <[email protected]>
Acked-by: Vineet Gupta <[email protected]>
Acked-by: Jesper Nilsson <[email protected]>
Acked-by: Vineet Gupta <[email protected]>
Acked-by: Martin Schwidefsky <[email protected]>	[s390 bits]
Cc: Heiko Carstens <[email protected]>
Cc: Mike Frysinger <[email protected]>
Cc: Fengguang Wu <[email protected]>
Cc: Bjorn Helgaas <[email protected]>
Cc: Sam Ravnborg <[email protected]>
Acked-by: Richard Kuo <[email protected]>		[hexagon bits]
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

Author: htejun

arch/alpha/kernel/traps.c

@@ -169,13 +169,6 @@ void show_stack(struct task_struct *task, unsigned long *sp)
 	dik_show_trace(sp);
 }
 
-void dump_stack(void)
-{
-	show_stack(NULL, NULL);
-}
-
-EXPORT_SYMBOL(dump_stack);
-
 void
 die_if_kernel(char * str, struct pt_regs *regs, long err, unsigned long *r9_15)
 {

arch/arc/kernel/stacktrace.c

@@ -220,13 +220,6 @@ void show_stack(struct task_struct *tsk, unsigned long *sp)
 	show_stacktrace(tsk, NULL);
 }
 
-/* Expected by Rest of kernel code */
-void dump_stack(void)
-{
-	show_stacktrace(NULL, NULL);
-}
-EXPORT_SYMBOL(dump_stack);
-
 /* Another API expected by schedular, shows up in "ps" as Wait Channel
  * Ofcourse just returning schedule( ) would be pointless so unwind until
  * the function is not in schedular code

arch/arm/kernel/traps.c

@@ -204,13 +204,6 @@ static void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk)
 }
 #endif
 
-void dump_stack(void)
-{
-	dump_backtrace(NULL, NULL);
-}
-
-EXPORT_SYMBOL(dump_stack);
-
 void show_stack(struct task_struct *tsk, unsigned long *sp)
 {
 	dump_backtrace(NULL, tsk);

arch/arm64/kernel/traps.c

@@ -167,13 +167,6 @@ static void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk)
 	}
 }
 
-void dump_stack(void)
-{
-	dump_backtrace(NULL, NULL);
-}
-
-EXPORT_SYMBOL(dump_stack);
-
 void show_stack(struct task_struct *tsk, unsigned long *sp)
 {
 	dump_backtrace(NULL, tsk);

arch/avr32/kernel/process.c

@@ -204,14 +204,6 @@ void show_stack(struct task_struct *tsk, unsigned long *stack)
 	show_stack_log_lvl(tsk, (unsigned long)stack, NULL, "");
 }
 
-void dump_stack(void)
-{
-	unsigned long stack;
-
-	show_trace_log_lvl(current, &stack, NULL, "");
-}
-EXPORT_SYMBOL(dump_stack);
-
 static const char *cpu_modes[] = {
 	"Application", "Supervisor", "Interrupt level 0", "Interrupt level 1",
 	"Interrupt level 2", "Interrupt level 3", "Exception", "NMI"

arch/blackfin/kernel/dumpstack.c

@@ -168,6 +168,7 @@ void dump_stack(void)
 #endif
 	trace_buffer_save(tflags);
 	dump_bfin_trace_buffer();
+	dump_stack_print_info(KERN_DEFAULT);
 	show_stack(current, &stack);
 	trace_buffer_restore(tflags);
 }

arch/c6x/kernel/traps.c

@@ -67,15 +67,6 @@ void show_regs(struct pt_regs *regs)
 	pr_err("A31: %08lx  B31: %08lx\n", regs->a31, regs->b31);
 }
 
-void dump_stack(void)
-{
-	unsigned long stack;
-
-	show_stack(current, &stack);
-}
-EXPORT_SYMBOL(dump_stack);
-
-
 void die(char *str, struct pt_regs *fp, int nr)
 {
 	console_verbose();

arch/cris/kernel/traps.c

@@ -146,13 +146,6 @@ show_stack(void)
 }
 #endif
 
-void
-dump_stack(void)
-{
-	show_stack(NULL, NULL);
-}
-EXPORT_SYMBOL(dump_stack);
-
 void
 set_nmi_handler(void (*handler)(struct pt_regs *))
 {

arch/frv/kernel/traps.c

@@ -466,17 +466,6 @@ asmlinkage void compound_exception(unsigned long esfr1,
 	BUG();
 } /* end compound_exception() */
 
-/*****************************************************************************/
-/*
- * The architecture-independent backtrace generator
- */
-void dump_stack(void)
-{
-	show_stack(NULL, NULL);
-}
-
-EXPORT_SYMBOL(dump_stack);
-
 void show_stack(struct task_struct *task, unsigned long *sp)
 {
 }

arch/h8300/kernel/traps.c

@@ -164,10 +164,3 @@ void show_trace_task(struct task_struct *tsk)
 {
 	show_stack(tsk,(unsigned long *)tsk->thread.esp0);
 }
-
-void dump_stack(void)
-{
-	show_stack(NULL,NULL);
-}
-
-EXPORT_SYMBOL(dump_stack);