1 files changed, 99 insertions, 98 deletions

diff --git a/drivers/oprofile/cpu_buffer.c b/drivers/oprofile/cpu_buffer.c
index 01d38e78cde1..61090969158f 100644
--- a/drivers/oprofile/cpu_buffer.c
+++ b/drivers/oprofile/cpu_buffer.c
@@ -28,6 +28,25 @@
 #include "buffer_sync.h"
 #include "oprof.h"
 
+#define OP_BUFFER_FLAGS 0
+
+/*
+ * Read and write access is using spin locking. Thus, writing to the
+ * buffer by NMI handler (x86) could occur also during critical
+ * sections when reading the buffer. To avoid this, there are 2
+ * buffers for independent read and write access. Read access is in
+ * process context only, write access only in the NMI handler. If the
+ * read buffer runs empty, both buffers are swapped atomically. There
+ * is potentially a small window during swapping where the buffers are
+ * disabled and samples could be lost.
+ *
+ * Using 2 buffers is a little bit overhead, but the solution is clear
+ * and does not require changes in the ring buffer implementation. It
+ * can be changed to a single buffer solution when the ring buffer
+ * access is implemented as non-locking atomic code.
+ */
+struct ring_buffer *op_ring_buffer_read;
+struct ring_buffer *op_ring_buffer_write;
 DEFINE_PER_CPU(struct oprofile_cpu_buffer, cpu_buffer);
 
 static void wq_sync_buffer(struct work_struct *work);
@@ -37,12 +56,12 @@ static int work_enabled;
 
 void free_cpu_buffers(void)
 {
-        int i;
-
-        for_each_possible_cpu(i) {
-                vfree(per_cpu(cpu_buffer, i).buffer);
-                per_cpu(cpu_buffer, i).buffer = NULL;
-        }
+        if (op_ring_buffer_read)
+                ring_buffer_free(op_ring_buffer_read);
+        op_ring_buffer_read = NULL;
+        if (op_ring_buffer_write)
+                ring_buffer_free(op_ring_buffer_write);
+        op_ring_buffer_write = NULL;
 }
 
 unsigned long oprofile_get_cpu_buffer_size(void)
@@ -64,14 +83,16 @@ int alloc_cpu_buffers(void)
 
         unsigned long buffer_size = fs_cpu_buffer_size;
 
+        op_ring_buffer_read = ring_buffer_alloc(buffer_size, OP_BUFFER_FLAGS);
+        if (!op_ring_buffer_read)
+                goto fail;
+        op_ring_buffer_write = ring_buffer_alloc(buffer_size, OP_BUFFER_FLAGS);
+        if (!op_ring_buffer_write)
+                goto fail;
+
         for_each_possible_cpu(i) {
                 struct oprofile_cpu_buffer *b = &per_cpu(cpu_buffer, i);
 
-                b->buffer = vmalloc_node(sizeof(struct op_sample) * buffer_size,
-                        cpu_to_node(i));
-                if (!b->buffer)
-                        goto fail;
-
                 b->last_task = NULL;
                 b->last_is_kernel = -1;
                 b->tracing = 0;
@@ -124,57 +145,31 @@ void end_cpu_work(void)
         flush_scheduled_work();
 }
 
-/* Resets the cpu buffer to a sane state. */
-void cpu_buffer_reset(struct oprofile_cpu_buffer *cpu_buf)
-{
-        /* reset these to invalid values; the next sample
-         * collected will populate the buffer with proper
-         * values to initialize the buffer
-         */
-        cpu_buf->last_is_kernel = -1;
-        cpu_buf->last_task = NULL;
-}
-
-/* compute number of available slots in cpu_buffer queue */
-static unsigned long nr_available_slots(struct oprofile_cpu_buffer const *b)
+static inline int
+add_sample(struct oprofile_cpu_buffer *cpu_buf,
+           unsigned long pc, unsigned long event)
 {
-        unsigned long head = b->head_pos;
-        unsigned long tail = b->tail_pos;
+        struct op_entry entry;
+        int ret;
 
-        if (tail > head)
-                return (tail - head) - 1;
+        ret = cpu_buffer_write_entry(&entry);
+        if (ret)
+                return ret;
 
-        return tail + (b->buffer_size - head) - 1;
-}
+        entry.sample->eip = pc;
+        entry.sample->event = event;
 
-static void increment_head(struct oprofile_cpu_buffer *b)
-{
-        unsigned long new_head = b->head_pos + 1;
-
-        /* Ensure anything written to the slot before we
-         * increment is visible */
-        wmb();
-
-        if (new_head < b->buffer_size)
-                b->head_pos = new_head;
-        else
-                b->head_pos = 0;
-}
+        ret = cpu_buffer_write_commit(&entry);
+        if (ret)
+                return ret;
 
-static inline void
-add_sample(struct oprofile_cpu_buffer *cpu_buf,
-           unsigned long pc, unsigned long event)
-{
-        struct op_sample *entry = &cpu_buf->buffer[cpu_buf->head_pos];
-        entry->eip = pc;
-        entry->event = event;
-        increment_head(cpu_buf);
+        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
@@ -198,11 +193,6 @@ static int log_sample(struct oprofile_cpu_buffer *cpu_buf, unsigned long pc,
                 return 0;
         }
 
-        if (nr_available_slots(cpu_buf) < 3) {
-                cpu_buf->sample_lost_overflow++;
-                return 0;
-        }
-
         is_kernel = !!is_kernel;
 
         task = current;
@@ -210,26 +200,29 @@ 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)
 {
-        if (nr_available_slots(cpu_buf) < 4) {
-                cpu_buf->sample_lost_overflow++;
-                return 0;
-        }
-
         add_code(cpu_buf, CPU_TRACE_BEGIN);
         cpu_buf->tracing = 1;
         return 1;
@@ -253,8 +246,10 @@ void oprofile_add_ext_sample(unsigned long pc, struct pt_regs * const regs,
         if (!oprofile_begin_trace(cpu_buf))
                 return;
 
-        /* if log_sample() fail we can't backtrace since we lost the source
-         * of this event */
+        /*
+         * if log_sample() fail we can't backtrace since we lost the
+         * source of this event
+         */
         if (log_sample(cpu_buf, pc, is_kernel, event))
                 oprofile_ops.backtrace(regs, backtrace_depth);
         oprofile_end_trace(cpu_buf);
@@ -272,49 +267,55 @@ void oprofile_add_sample(struct pt_regs * const regs, unsigned long event)
 
 #define MAX_IBS_SAMPLE_SIZE 14
 
-void oprofile_add_ibs_sample(struct pt_regs *const regs,
-                             unsigned int *const ibs_sample, int ibs_code)
+void oprofile_add_ibs_sample(struct pt_regs * const regs,
+                             unsigned int * const ibs_sample, int ibs_code)
 {
         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++;
 
-        if (nr_available_slots(cpu_buf) < MAX_IBS_SAMPLE_SIZE) {
-                /* we can't backtrace since we lost the source of this event */
-                cpu_buf->sample_lost_overflow++;
-                return;
-        }
-
         /* 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
@@ -332,21 +333,21 @@ void oprofile_add_trace(unsigned long pc)
         if (!cpu_buf->tracing)
                 return;
 
-        if (nr_available_slots(cpu_buf) < 1) {
-                cpu_buf->tracing = 0;
-                cpu_buf->sample_lost_overflow++;
-                return;
-        }
+        /*
+         * 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)
+                goto fail;
 
-        /* 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 (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;
 }
 
 /*