oprofile: fix lost sample counter

The number of lost samples could be greater than the number of
received samples. This patches fixes this. The implementation
introduces return values for add_sample() and add_code().

Signed-off-by: Robert Richter <robert.richter@amd.com>

diff --git a/drivers/oprofile/cpu_buffer.c b/drivers/oprofile/cpu_buffer.c
index 7f7fc95..6109096 100644 (file)
--- a/drivers/oprofile/cpu_buffer.c
+++ b/drivers/oprofile/cpu_buffer.c
@@ -145,32 +145,31 @@ void end_cpu_work(void)
        flush_scheduled_work();
 }
 
-static inline void
+static inline int
 add_sample(struct oprofile_cpu_buffer *cpu_buf,
           unsigned long pc, unsigned long event)
 {
        struct op_entry entry;
+       int ret;
 
-       if (cpu_buffer_write_entry(&entry))
-               goto Error;
+       ret = cpu_buffer_write_entry(&entry);
+       if (ret)
+               return ret;
 
        entry.sample->eip = pc;
        entry.sample->event = event;
 
-       if (cpu_buffer_write_commit(&entry))
-               goto Error;
+       ret = cpu_buffer_write_commit(&entry);
+       if (ret)
+               return ret;
 
-       return;
-
-Error:
-       cpu_buf->sample_lost_overflow++;
-       return;
+       return 0;
 }
 
-static inline void
+static inline int
 add_code(struct oprofile_cpu_buffer *buffer, unsigned long value)
 {
-       add_sample(buffer, ESCAPE_CODE, value);
+       return add_sample(buffer, ESCAPE_CODE, value);
 }
 
 /* This must be safe from any context. It's safe writing here
@@ -201,17 +200,25 @@ static int log_sample(struct oprofile_cpu_buffer *cpu_buf, unsigned long pc,
        /* notice a switch from user->kernel or vice versa */
        if (cpu_buf->last_is_kernel != is_kernel) {
                cpu_buf->last_is_kernel = is_kernel;
-               add_code(cpu_buf, is_kernel);
+               if (add_code(cpu_buf, is_kernel))
+                       goto fail;
        }
 
        /* notice a task switch */
        if (cpu_buf->last_task != task) {
                cpu_buf->last_task = task;
-               add_code(cpu_buf, (unsigned long)task);
+               if (add_code(cpu_buf, (unsigned long)task))
+                       goto fail;
        }
 
-       add_sample(cpu_buf, pc, event);
+       if (add_sample(cpu_buf, pc, event))
+               goto fail;
+
        return 1;
+
+fail:
+       cpu_buf->sample_lost_overflow++;
+       return 0;
 }
 
 static int oprofile_begin_trace(struct oprofile_cpu_buffer *cpu_buf)
@@ -266,37 +273,49 @@ void oprofile_add_ibs_sample(struct pt_regs * const regs,
        int is_kernel = !user_mode(regs);
        struct oprofile_cpu_buffer *cpu_buf = &__get_cpu_var(cpu_buffer);
        struct task_struct *task;
+       int fail = 0;
 
        cpu_buf->sample_received++;
 
        /* notice a switch from user->kernel or vice versa */
        if (cpu_buf->last_is_kernel != is_kernel) {
+               if (add_code(cpu_buf, is_kernel))
+                       goto fail;
                cpu_buf->last_is_kernel = is_kernel;
-               add_code(cpu_buf, is_kernel);
        }
 
        /* notice a task switch */
        if (!is_kernel) {
                task = current;
                if (cpu_buf->last_task != task) {
+                       if (add_code(cpu_buf, (unsigned long)task))
+                               goto fail;
                        cpu_buf->last_task = task;
-                       add_code(cpu_buf, (unsigned long)task);
                }
        }
 
-       add_code(cpu_buf, ibs_code);
-       add_sample(cpu_buf, ibs_sample[0], ibs_sample[1]);
-       add_sample(cpu_buf, ibs_sample[2], ibs_sample[3]);
-       add_sample(cpu_buf, ibs_sample[4], ibs_sample[5]);
+       fail = fail || add_code(cpu_buf, ibs_code);
+       fail = fail || add_sample(cpu_buf, ibs_sample[0], ibs_sample[1]);
+       fail = fail || add_sample(cpu_buf, ibs_sample[2], ibs_sample[3]);
+       fail = fail || add_sample(cpu_buf, ibs_sample[4], ibs_sample[5]);
 
        if (ibs_code == IBS_OP_BEGIN) {
-               add_sample(cpu_buf, ibs_sample[6], ibs_sample[7]);
-               add_sample(cpu_buf, ibs_sample[8], ibs_sample[9]);
-               add_sample(cpu_buf, ibs_sample[10], ibs_sample[11]);
+               fail = fail || add_sample(cpu_buf, ibs_sample[6], ibs_sample[7]);
+               fail = fail || add_sample(cpu_buf, ibs_sample[8], ibs_sample[9]);
+               fail = fail || add_sample(cpu_buf, ibs_sample[10], ibs_sample[11]);
        }
 
+       if (fail)
+               goto fail;
+
        if (backtrace_depth)
                oprofile_ops.backtrace(regs, backtrace_depth);
+
+       return;
+
+fail:
+       cpu_buf->sample_lost_overflow++;
+       return;
 }
 
 #endif
@@ -318,13 +337,17 @@ void oprofile_add_trace(unsigned long pc)
         * broken frame can give an eip with the same value as an
         * escape code, abort the trace if we get it
         */
-       if (pc == ESCAPE_CODE) {
-               cpu_buf->tracing = 0;
-               cpu_buf->backtrace_aborted++;
-               return;
-       }
+       if (pc == ESCAPE_CODE)
+               goto fail;
+
+       if (add_sample(cpu_buf, pc, 0))
+               goto fail;
 
-       add_sample(cpu_buf, pc, 0);
+       return;
+fail:
+       cpu_buf->tracing = 0;
+       cpu_buf->backtrace_aborted++;
+       return;
 }
 
 /*