3 files changed, 114 insertions, 85 deletions

diff --git a/drivers/oprofile/buffer_sync.c b/drivers/oprofile/buffer_sync.c
index 944a5832d9e4..737bd9484822 100644
--- a/drivers/oprofile/buffer_sync.c
+++ b/drivers/oprofile/buffer_sync.c
@@ -268,18 +268,6 @@ lookup_dcookie(struct mm_struct *mm, unsigned long addr, off_t *offset)
         return cookie;
 }
 
-static void increment_tail(struct oprofile_cpu_buffer *b)
-{
-        unsigned long new_tail = b->tail_pos + 1;
-
-        rmb();  /* be sure fifo pointers are synchronized */
-
-        if (new_tail < b->buffer_size)
-                b->tail_pos = new_tail;
-        else
-                b->tail_pos = 0;
-}
-
 static unsigned long last_cookie = INVALID_COOKIE;
 
 static void add_cpu_switch(int i)
@@ -331,26 +319,25 @@ static void add_trace_begin(void)
 
 #define IBS_FETCH_CODE_SIZE     2
 #define IBS_OP_CODE_SIZE        5
-#define IBS_EIP(cpu_buf)        ((cpu_buffer_read_entry(cpu_buf))->eip)
-#define IBS_EVENT(cpu_buf)      ((cpu_buffer_read_entry(cpu_buf))->event)
 
 /*
  * Add IBS fetch and op entries to event buffer
  */
-static void add_ibs_begin(struct oprofile_cpu_buffer *cpu_buf, int code,
-                          struct mm_struct *mm)
+static void add_ibs_begin(int cpu, int code, struct mm_struct *mm)
 {
         unsigned long rip;
         int i, count;
         unsigned long ibs_cookie = 0;
         off_t offset;
+        struct op_sample *sample;
 
-        increment_tail(cpu_buf);        /* move to RIP entry */
-
-        rip = IBS_EIP(cpu_buf);
+        sample = cpu_buffer_read_entry(cpu);
+        if (!sample)
+                goto Error;
+        rip = sample->eip;
 
 #ifdef __LP64__
-        rip += IBS_EVENT(cpu_buf) << 32;
+        rip += sample->event << 32;
 #endif
 
         if (mm) {
@@ -374,8 +361,8 @@ static void add_ibs_begin(struct oprofile_cpu_buffer *cpu_buf, int code,
         add_event_entry(offset);        /* Offset from Dcookie */
 
         /* we send the Dcookie offset, but send the raw Linear Add also*/
-        add_event_entry(IBS_EIP(cpu_buf));
-        add_event_entry(IBS_EVENT(cpu_buf));
+        add_event_entry(sample->eip);
+        add_event_entry(sample->event);
 
         if (code == IBS_FETCH_CODE)
                 count = IBS_FETCH_CODE_SIZE;    /*IBS FETCH is 2 int64s*/
@@ -383,10 +370,17 @@ static void add_ibs_begin(struct oprofile_cpu_buffer *cpu_buf, int code,
                 count = IBS_OP_CODE_SIZE;       /*IBS OP is 5 int64s*/
 
         for (i = 0; i < count; i++) {
-                increment_tail(cpu_buf);
-                add_event_entry(IBS_EIP(cpu_buf));
-                add_event_entry(IBS_EVENT(cpu_buf));
+                sample = cpu_buffer_read_entry(cpu);
+                if (!sample)
+                        goto Error;
+                add_event_entry(sample->eip);
+                add_event_entry(sample->event);
         }
+
+        return;
+
+Error:
+        return;
 }
 
 #endif
@@ -530,33 +524,26 @@ typedef enum {
  */
 void sync_buffer(int cpu)
 {
-        struct oprofile_cpu_buffer *cpu_buf = &per_cpu(cpu_buffer, cpu);
         struct mm_struct *mm = NULL;
         struct mm_struct *oldmm;
         struct task_struct *new;
         unsigned long cookie = 0;
         int in_kernel = 1;
         sync_buffer_state state = sb_buffer_start;
-#ifndef CONFIG_OPROFILE_IBS
         unsigned int i;
         unsigned long available;
-#endif
 
         mutex_lock(&buffer_mutex);
 
         add_cpu_switch(cpu);
 
-        /* Remember, only we can modify tail_pos */
-
         cpu_buffer_reset(cpu);
-#ifndef CONFIG_OPROFILE_IBS
-        available = cpu_buffer_entries(cpu_buf);
+        available = cpu_buffer_entries(cpu);
 
         for (i = 0; i < available; ++i) {
-#else
-        while (cpu_buffer_entries(cpu_buf)) {
-#endif
-                struct op_sample *s = cpu_buffer_read_entry(cpu_buf);
+                struct op_sample *s = cpu_buffer_read_entry(cpu);
+                if (!s)
+                        break;
 
                 if (is_code(s->eip)) {
                         switch (s->event) {
@@ -575,11 +562,11 @@ void sync_buffer(int cpu)
 #ifdef CONFIG_OPROFILE_IBS
                         case IBS_FETCH_BEGIN:
                                 state = sb_bt_start;
-                                add_ibs_begin(cpu_buf, IBS_FETCH_CODE, mm);
+                                add_ibs_begin(cpu, IBS_FETCH_CODE, mm);
                                 break;
                         case IBS_OP_BEGIN:
                                 state = sb_bt_start;
-                                add_ibs_begin(cpu_buf, IBS_OP_CODE, mm);
+                                add_ibs_begin(cpu, IBS_OP_CODE, mm);
                                 break;
 #endif
                         default:
@@ -600,8 +587,6 @@ void sync_buffer(int cpu)
                                 atomic_inc(&oprofile_stats.bt_lost_no_mapping);
                         }
                 }
-
-                increment_tail(cpu_buf);
         }
         release_mm(mm);
 
diff --git a/drivers/oprofile/cpu_buffer.c b/drivers/oprofile/cpu_buffer.c
index 5cf7efe38e67..eb280ec96e24 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;
@@ -140,10 +161,22 @@ static inline void
 add_sample(struct oprofile_cpu_buffer *cpu_buf,
            unsigned long pc, unsigned long event)
 {
-        struct op_sample *entry = cpu_buffer_write_entry(cpu_buf);
-        entry->eip = pc;
-        entry->event = event;
-        cpu_buffer_write_commit(cpu_buf);
+        struct op_entry entry;
+
+        if (cpu_buffer_write_entry(&entry))
+                goto Error;
+
+        entry.sample->eip = pc;
+        entry.sample->event = event;
+
+        if (cpu_buffer_write_commit(&entry))
+                goto Error;
+
+        return;
+
+Error:
+        cpu_buf->sample_lost_overflow++;
+        return;
 }
 
 static inline void
diff --git a/drivers/oprofile/cpu_buffer.h b/drivers/oprofile/cpu_buffer.h
index 895763f065e9..aacb0f0bc566 100644
--- a/drivers/oprofile/cpu_buffer.h
+++ b/drivers/oprofile/cpu_buffer.h
@@ -15,6 +15,7 @@
 #include <linux/workqueue.h>
 #include <linux/cache.h>
 #include <linux/sched.h>
+#include <linux/ring_buffer.h>
 
 struct task_struct;
 
@@ -32,6 +33,12 @@ struct op_sample {
         unsigned long event;
 };
 
+struct op_entry {
+        struct ring_buffer_event *event;
+        struct op_sample *sample;
+        unsigned long irq_flags;
+};
+
 struct oprofile_cpu_buffer {
         volatile unsigned long head_pos;
         volatile unsigned long tail_pos;
@@ -39,7 +46,6 @@ struct oprofile_cpu_buffer {
         struct task_struct *last_task;
         int last_is_kernel;
         int tracing;
-        struct op_sample *buffer;
         unsigned long sample_received;
         unsigned long sample_lost_overflow;
         unsigned long backtrace_aborted;
@@ -48,6 +54,8 @@ struct oprofile_cpu_buffer {
         struct delayed_work work;
 };
 
+extern struct ring_buffer *op_ring_buffer_read;
+extern struct ring_buffer *op_ring_buffer_write;
 DECLARE_PER_CPU(struct oprofile_cpu_buffer, cpu_buffer);
 
 /*
@@ -64,46 +72,49 @@ static inline void cpu_buffer_reset(int cpu)
         cpu_buf->last_task = NULL;
 }
 
-static inline
-struct op_sample *cpu_buffer_write_entry(struct oprofile_cpu_buffer *cpu_buf)
+static inline int cpu_buffer_write_entry(struct op_entry *entry)
 {
-        return &cpu_buf->buffer[cpu_buf->head_pos];
-}
+        entry->event = ring_buffer_lock_reserve(op_ring_buffer_write,
+                                                sizeof(struct op_sample),
+                                                &entry->irq_flags);
+        if (entry->event)
+                entry->sample = ring_buffer_event_data(entry->event);
+        else
+                entry->sample = NULL;
 
-static inline
-void cpu_buffer_write_commit(struct oprofile_cpu_buffer *b)
-{
-        unsigned long new_head = b->head_pos + 1;
+        if (!entry->sample)
+                return -ENOMEM;
 
-        /*
-         * Ensure anything written to the slot before we increment is
-         * visible
-         */
-        wmb();
+        return 0;
+}
 
-        if (new_head < b->buffer_size)
-                b->head_pos = new_head;
-        else
-                b->head_pos = 0;
+static inline int cpu_buffer_write_commit(struct op_entry *entry)
+{
+        return ring_buffer_unlock_commit(op_ring_buffer_write, entry->event,
+                                         entry->irq_flags);
 }
 
-static inline
-struct op_sample *cpu_buffer_read_entry(struct oprofile_cpu_buffer *cpu_buf)
+static inline struct op_sample *cpu_buffer_read_entry(int cpu)
 {
-        return &cpu_buf->buffer[cpu_buf->tail_pos];
+        struct ring_buffer_event *e;
+        e = ring_buffer_consume(op_ring_buffer_read, cpu, NULL);
+        if (e)
+                return ring_buffer_event_data(e);
+        if (ring_buffer_swap_cpu(op_ring_buffer_read,
+                                 op_ring_buffer_write,
+                                 cpu))
+                return NULL;
+        e = ring_buffer_consume(op_ring_buffer_read, cpu, NULL);
+        if (e)
+                return ring_buffer_event_data(e);
+        return NULL;
 }
 
 /* "acquire" as many cpu buffer slots as we can */
-static inline
-unsigned long cpu_buffer_entries(struct oprofile_cpu_buffer *b)
+static inline unsigned long cpu_buffer_entries(int cpu)
 {
-        unsigned long head = b->head_pos;
-        unsigned long tail = b->tail_pos;
-
-        if (head >= tail)
-                return head - tail;
-
-        return head + (b->buffer_size - tail);
+        return ring_buffer_entries_cpu(op_ring_buffer_read, cpu)
+                + ring_buffer_entries_cpu(op_ring_buffer_write, cpu);
 }
 
 /* transient events for the CPU buffer -> event buffer */