[ARM] latencytop support

Available for !SMP only at the moment.

From Russell:

|Basically, if a thread is running on a CPU, thread_saved_fp() is invalid.
|So, the question is: what guarantees do we have here that 'tsk' is not
|running on another CPU?

Signed-off-by: Nicolas Pitre <nico@marvell.com>
Tested-by: Lennert Buytenhek <buytenh@marvell.com>
Signed-off-by: Lennert Buytenhek <buytenh@marvell.com>

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index b786e68..a91b9ac 100644 (file)
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -84,6 +84,11 @@ config STACKTRACE_SUPPORT
        bool
        default y
 
+config HAVE_LATENCYTOP_SUPPORT
+       bool
+       depends on !SMP
+       default y
+
 config LOCKDEP_SUPPORT
        bool
        default y

diff --git a/arch/arm/kernel/stacktrace.c b/arch/arm/kernel/stacktrace.c
index ae31deb..90e0c35 100644 (file)
--- a/arch/arm/kernel/stacktrace.c
+++ b/arch/arm/kernel/stacktrace.c
@@ -36,6 +36,7 @@ EXPORT_SYMBOL(walk_stackframe);
 #ifdef CONFIG_STACKTRACE
 struct stack_trace_data {
        struct stack_trace *trace;
+       unsigned int no_sched_functions;
        unsigned int skip;
 };
 
@@ -43,27 +44,52 @@ static int save_trace(struct stackframe *frame, void *d)
 {
        struct stack_trace_data *data = d;
        struct stack_trace *trace = data->trace;
+       unsigned long addr = frame->lr;
 
+       if (data->no_sched_functions && in_sched_functions(addr))
+               return 0;
        if (data->skip) {
                data->skip--;
                return 0;
        }
 
-       trace->entries[trace->nr_entries++] = frame->lr;
+       trace->entries[trace->nr_entries++] = addr;
 
        return trace->nr_entries >= trace->max_entries;
 }
 
-void save_stack_trace(struct stack_trace *trace)
+void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
 {
        struct stack_trace_data data;
        unsigned long fp, base;
 
        data.trace = trace;
        data.skip = trace->skip;
-       base = (unsigned long)task_stack_page(current);
-       asm("mov %0, fp" : "=r" (fp));
+       base = (unsigned long)task_stack_page(tsk);
+
+       if (tsk != current) {
+#ifdef CONFIG_SMP
+               /*
+                * What guarantees do we have here that 'tsk'
+                * is not running on another CPU?
+                */
+               BUG();
+#else
+               data.no_sched_functions = 1;
+               fp = thread_saved_fp(tsk);
+#endif
+       } else {
+               data.no_sched_functions = 0;
+               asm("mov %0, fp" : "=r" (fp));
+       }
 
        walk_stackframe(fp, base, base + THREAD_SIZE, save_trace, &data);
+       if (trace->nr_entries < trace->max_entries)
+               trace->entries[trace->nr_entries++] = ULONG_MAX;
+}
+
+void save_stack_trace(struct stack_trace *trace)
+{
+       save_stack_trace_tsk(current, trace);
 }
 #endif