simplify the stacktrace code

Simplify the stacktrace code:

 - remove the unused task argument to save_stack_trace, it's always
   current
 - remove the all_contexts flag, it's alwasy 0

Signed-off-by: Christoph Hellwig <hch@lst.de>
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Andi Kleen <ak@suse.de>
Cc: Akinobu Mita <akinobu.mita@gmail.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

8 files changed, 28 insertions, 61 deletions

diff --git a/arch/mips/kernel/stacktrace.c b/arch/mips/kernel/stacktrace.c
index a586aba337a7..ebd9db8d1ece 100644
--- a/arch/mips/kernel/stacktrace.c
+++ b/arch/mips/kernel/stacktrace.c
@@ -31,8 +31,7 @@ static void save_raw_context_stack(struct stack_trace *trace,
         }
 }
 
-static void save_context_stack(struct stack_trace *trace,
-        struct task_struct *task, struct pt_regs *regs)
+static void save_context_stack(struct stack_trace *trace, struct pt_regs *regs)
 {
         unsigned long sp = regs->regs[29];
 #ifdef CONFIG_KALLSYMS
@@ -41,7 +40,7 @@ static void save_context_stack(struct stack_trace *trace,
 
         if (raw_show_trace || !__kernel_text_address(pc)) {
                 unsigned long stack_page =
-                        (unsigned long)task_stack_page(task);
+                        (unsigned long)task_stack_page(current);
                 if (stack_page && sp >= stack_page &&
                     sp <= stack_page + THREAD_SIZE - 32)
                         save_raw_context_stack(trace, sp);
@@ -54,7 +53,7 @@ static void save_context_stack(struct stack_trace *trace,
                         trace->entries[trace->nr_entries++] = pc;
                 if (trace->nr_entries >= trace->max_entries)
                         break;
-                pc = unwind_stack(task, &sp, pc, &ra);
+                pc = unwind_stack(current, &sp, pc, &ra);
         } while (pc);
 #else
         save_raw_context_stack(trace, sp);
@@ -64,22 +63,13 @@ static void save_context_stack(struct stack_trace *trace,
 /*
  * Save stack-backtrace addresses into a stack_trace buffer.
  */
-void save_stack_trace(struct stack_trace *trace, struct task_struct *task)
+void save_stack_trace(struct stack_trace *trace)
 {
         struct pt_regs dummyregs;
         struct pt_regs *regs = &dummyregs;
 
         WARN_ON(trace->nr_entries || !trace->max_entries);
 
-        if (task && task != current) {
-                regs->regs[29] = task->thread.reg29;
-                regs->regs[31] = 0;
-                regs->cp0_epc = task->thread.reg31;
-        } else {
-                if (!task)
-                        task = current;
-                prepare_frametrace(regs);
-        }
-
-        save_context_stack(trace, task, regs);
+        prepare_frametrace(regs);
+        save_context_stack(trace, regs);
 }
diff --git a/arch/s390/kernel/stacktrace.c b/arch/s390/kernel/stacktrace.c
index 2e5c65a1863e..515ff9011dd7 100644
--- a/arch/s390/kernel/stacktrace.c
+++ b/arch/s390/kernel/stacktrace.c
@@ -59,7 +59,7 @@ static unsigned long save_context_stack(struct stack_trace *trace,
         }
 }
 
-void save_stack_trace(struct stack_trace *trace, struct task_struct *task)
+void save_stack_trace(struct stack_trace *trace)
 {
         register unsigned long sp asm ("15");
         unsigned long orig_sp, new_sp;
@@ -69,20 +69,16 @@ void save_stack_trace(struct stack_trace *trace, struct task_struct *task)
         new_sp = save_context_stack(trace, &trace->skip, orig_sp,
                                 S390_lowcore.panic_stack - PAGE_SIZE,
                                 S390_lowcore.panic_stack);
-        if ((new_sp != orig_sp) && !trace->all_contexts)
+        if (new_sp != orig_sp)
                 return;
         new_sp = save_context_stack(trace, &trace->skip, new_sp,
                                 S390_lowcore.async_stack - ASYNC_SIZE,
                                 S390_lowcore.async_stack);
-        if ((new_sp != orig_sp) && !trace->all_contexts)
+        if (new_sp != orig_sp)
                 return;
-        if (task)
-                save_context_stack(trace, &trace->skip, new_sp,
-                                   (unsigned long) task_stack_page(task),
-                                   (unsigned long) task_stack_page(task) + THREAD_SIZE);
-        else
-                save_context_stack(trace, &trace->skip, new_sp,
-                                   S390_lowcore.thread_info,
-                                   S390_lowcore.thread_info + THREAD_SIZE);
+
+        save_context_stack(trace, &trace->skip, new_sp,
+                           S390_lowcore.thread_info,
+                           S390_lowcore.thread_info + THREAD_SIZE);
         return;
 }
diff --git a/arch/sh/kernel/stacktrace.c b/arch/sh/kernel/stacktrace.c
index 0d5268afe80f..4bdd2f83535d 100644
--- a/arch/sh/kernel/stacktrace.c
+++ b/arch/sh/kernel/stacktrace.c
@@ -19,14 +19,7 @@
  */
 void save_stack_trace(struct stack_trace *trace, struct task_struct *task)
 {
-        unsigned long *sp;
-
-        if (!task)
-                task = current;
-        if (task == current)
-                sp = (unsigned long *)current_stack_pointer;
-        else
-                sp = (unsigned long *)task->thread.sp;
+        unsigned long *sp = (unsigned long *)current_stack_pointer;
 
         while (!kstack_end(sp)) {
                 unsigned long addr = *sp++;
diff --git a/arch/sparc64/kernel/stacktrace.c b/arch/sparc64/kernel/stacktrace.c
index c4d15f2762b9..47f92a59be18 100644
--- a/arch/sparc64/kernel/stacktrace.c
+++ b/arch/sparc64/kernel/stacktrace.c
@@ -3,22 +3,16 @@
 #include <linux/thread_info.h>
 #include <asm/ptrace.h>
 
-void save_stack_trace(struct stack_trace *trace, struct task_struct *task)
+void save_stack_trace(struct stack_trace *trace)
 {
         unsigned long ksp, fp, thread_base;
-        struct thread_info *tp;
+        struct thread_info *tp = task_thread_info(current);
 
-        if (!task)
-                task = current;
-        tp = task_thread_info(task);
-        if (task == current) {
-                flushw_all();
-                __asm__ __volatile__(
-                        "mov    %%fp, %0"
-                        : "=r" (ksp)
-                );
-        } else
-                ksp = tp->ksp;
+        flushw_all();
+        __asm__ __volatile__(
+                "mov    %%fp, %0"
+                : "=r" (ksp)
+        );
 
         fp = ksp + STACK_BIAS;
         thread_base = (unsigned long) tp;
diff --git a/arch/x86_64/kernel/stacktrace.c b/arch/x86_64/kernel/stacktrace.c
index 65ac2c6b34a6..cb9109113584 100644
--- a/arch/x86_64/kernel/stacktrace.c
+++ b/arch/x86_64/kernel/stacktrace.c
@@ -21,8 +21,7 @@ save_stack_warning_symbol(void *data, char *msg, unsigned long symbol)
 
 static int save_stack_stack(void *data, char *name)
 {
-        struct stack_trace *trace = (struct stack_trace *)data;
-        return trace->all_contexts ? 0 : -1;
+        return -1;
 }
 
 static void save_stack_address(void *data, unsigned long addr)
@@ -46,11 +45,10 @@ static struct stacktrace_ops save_stack_ops = {
 /*
  * Save stack-backtrace addresses into a stack_trace buffer.
  */
-void save_stack_trace(struct stack_trace *trace, struct task_struct *task)
+void save_stack_trace(struct stack_trace *trace)
 {
-        dump_trace(task, NULL, NULL, &save_stack_ops, trace);
+        dump_trace(current, NULL, NULL, &save_stack_ops, trace);
         if (trace->nr_entries < trace->max_entries)
                 trace->entries[trace->nr_entries++] = ULONG_MAX;
 }
 EXPORT_SYMBOL(save_stack_trace);
-
diff --git a/include/linux/stacktrace.h b/include/linux/stacktrace.h
index 50e2b01e517c..1d2b084c0185 100644
--- a/include/linux/stacktrace.h
+++ b/include/linux/stacktrace.h
@@ -6,15 +6,13 @@ struct stack_trace {
         unsigned int nr_entries, max_entries;
         unsigned long *entries;
         int skip;       /* input argument: How many entries to skip */
-        int all_contexts; /* input argument: if true do than one stack */
 };
 
-extern void save_stack_trace(struct stack_trace *trace,
-                             struct task_struct *task);
+extern void save_stack_trace(struct stack_trace *trace);
 
 extern void print_stack_trace(struct stack_trace *trace, int spaces);
 #else
-# define save_stack_trace(trace, task)                  do { } while (0)
+# define save_stack_trace(trace)                        do { } while (0)
 # define print_stack_trace(trace)                       do { } while (0)
 #endif
 
diff --git a/kernel/lockdep.c b/kernel/lockdep.c
index 7065a687ac54..c1e308a080b8 100644
--- a/kernel/lockdep.c
+++ b/kernel/lockdep.c
@@ -257,9 +257,8 @@ static int save_trace(struct stack_trace *trace)
         trace->entries = stack_trace + nr_stack_trace_entries;
 
         trace->skip = 3;
-        trace->all_contexts = 0;
 
-        save_stack_trace(trace, NULL);
+        save_stack_trace(trace);
 
         trace->max_entries = trace->nr_entries;
 
diff --git a/lib/fault-inject.c b/lib/fault-inject.c
index 0fabd12c39d7..b18fc2ff9ffe 100644
--- a/lib/fault-inject.c
+++ b/lib/fault-inject.c
@@ -72,9 +72,8 @@ static bool fail_stacktrace(struct fault_attr *attr)
         trace.entries = entries;
         trace.max_entries = depth;
         trace.skip = 1;
-        trace.all_contexts = 0;
 
-        save_stack_trace(&trace, NULL);
+        save_stack_trace(&trace);
         for (n = 0; n < trace.nr_entries; n++) {
                 if (attr->reject_start <= entries[n] &&
                                entries[n] < attr->reject_end)