1 files changed, 131 insertions, 34 deletions

diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
index 45e6c01b2e4d..a43d009c561a 100644
--- a/kernel/trace/trace_functions_graph.c
+++ b/kernel/trace/trace_functions_graph.c
@@ -14,9 +14,20 @@
 #include "trace.h"
 #include "trace_output.h"
 
-struct fgraph_data {
+struct fgraph_cpu_data {
         pid_t           last_pid;
         int             depth;
+        int             ignore;
+};
+
+struct fgraph_data {
+        struct fgraph_cpu_data          *cpu_data;
+
+        /* Place to preserve last processed entry. */
+        struct ftrace_graph_ent_entry   ent;
+        struct ftrace_graph_ret_entry   ret;
+        int                             failed;
+        int                             cpu;
 };
 
 #define TRACE_GRAPH_INDENT      2
@@ -384,7 +395,7 @@ verif_pid(struct trace_seq *s, pid_t pid, int cpu, struct fgraph_data *data)
         if (!data)
                 return TRACE_TYPE_HANDLED;
 
-        last_pid = &(per_cpu_ptr(data, cpu)->last_pid);
+        last_pid = &(per_cpu_ptr(data->cpu_data, cpu)->last_pid);
 
         if (*last_pid == pid)
                 return TRACE_TYPE_HANDLED;
@@ -435,26 +446,49 @@ static struct ftrace_graph_ret_entry *
 get_return_for_leaf(struct trace_iterator *iter,
                 struct ftrace_graph_ent_entry *curr)
 {
-        struct ring_buffer_iter *ring_iter;
+        struct fgraph_data *data = iter->private;
+        struct ring_buffer_iter *ring_iter = NULL;
         struct ring_buffer_event *event;
         struct ftrace_graph_ret_entry *next;
 
-        ring_iter = iter->buffer_iter[iter->cpu];
+        /*
+         * If the previous output failed to write to the seq buffer,
+         * then we just reuse the data from before.
+         */
+        if (data && data->failed) {
+                curr = &data->ent;
+                next = &data->ret;
+        } else {
 
-        /* First peek to compare current entry and the next one */
-        if (ring_iter)
-                event = ring_buffer_iter_peek(ring_iter, NULL);
-        else {
-        /* We need to consume the current entry to see the next one */
-                ring_buffer_consume(iter->tr->buffer, iter->cpu, NULL);
-                event = ring_buffer_peek(iter->tr->buffer, iter->cpu,
-                                        NULL);
-        }
+                ring_iter = iter->buffer_iter[iter->cpu];
+
+                /* First peek to compare current entry and the next one */
+                if (ring_iter)
+                        event = ring_buffer_iter_peek(ring_iter, NULL);
+                else {
+                        /*
+                         * We need to consume the current entry to see
+                         * the next one.
+                         */
+                        ring_buffer_consume(iter->tr->buffer, iter->cpu, NULL);
+                        event = ring_buffer_peek(iter->tr->buffer, iter->cpu,
+                                                 NULL);
+                }
 
-        if (!event)
-                return NULL;
+                if (!event)
+                        return NULL;
+
+                next = ring_buffer_event_data(event);
 
-        next = ring_buffer_event_data(event);
+                if (data) {
+                        /*
+                         * Save current and next entries for later reference
+                         * if the output fails.
+                         */
+                        data->ent = *curr;
+                        data->ret = *next;
+                }
+        }
 
         if (next->ent.type != TRACE_GRAPH_RET)
                 return NULL;
@@ -640,7 +674,7 @@ print_graph_entry_leaf(struct trace_iterator *iter,
 
         if (data) {
                 int cpu = iter->cpu;
-                int *depth = &(per_cpu_ptr(data, cpu)->depth);
+                int *depth = &(per_cpu_ptr(data->cpu_data, cpu)->depth);
 
                 /*
                  * Comments display at + 1 to depth. Since
@@ -688,7 +722,7 @@ print_graph_entry_nested(struct trace_iterator *iter,
 
         if (data) {
                 int cpu = iter->cpu;
-                int *depth = &(per_cpu_ptr(data, cpu)->depth);
+                int *depth = &(per_cpu_ptr(data->cpu_data, cpu)->depth);
 
                 *depth = call->depth;
         }
@@ -782,19 +816,34 @@ static enum print_line_t
 print_graph_entry(struct ftrace_graph_ent_entry *field, struct trace_seq *s,
                         struct trace_iterator *iter)
 {
-        int cpu = iter->cpu;
+        struct fgraph_data *data = iter->private;
         struct ftrace_graph_ent *call = &field->graph_ent;
         struct ftrace_graph_ret_entry *leaf_ret;
+        static enum print_line_t ret;
+        int cpu = iter->cpu;
 
         if (print_graph_prologue(iter, s, TRACE_GRAPH_ENT, call->func))
                 return TRACE_TYPE_PARTIAL_LINE;
 
         leaf_ret = get_return_for_leaf(iter, field);
         if (leaf_ret)
-                return print_graph_entry_leaf(iter, field, leaf_ret, s);
+                ret = print_graph_entry_leaf(iter, field, leaf_ret, s);
         else
-                return print_graph_entry_nested(iter, field, s, cpu);
+                ret = print_graph_entry_nested(iter, field, s, cpu);
 
+        if (data) {
+                /*
+                 * If we failed to write our output, then we need to make
+                 * note of it. Because we already consumed our entry.
+                 */
+                if (s->full) {
+                        data->failed = 1;
+                        data->cpu = cpu;
+                } else
+                        data->failed = 0;
+        }
+
+        return ret;
 }
 
 static enum print_line_t
@@ -810,7 +859,7 @@ print_graph_return(struct ftrace_graph_ret *trace, struct trace_seq *s,
 
         if (data) {
                 int cpu = iter->cpu;
-                int *depth = &(per_cpu_ptr(data, cpu)->depth);
+                int *depth = &(per_cpu_ptr(data->cpu_data, cpu)->depth);
 
                 /*
                  * Comments display at + 1 to depth. This is the
@@ -873,7 +922,7 @@ print_graph_comment(struct trace_seq *s,  struct trace_entry *ent,
         int i;
 
         if (data)
-                depth = per_cpu_ptr(data, iter->cpu)->depth;
+                depth = per_cpu_ptr(data->cpu_data, iter->cpu)->depth;
 
         if (print_graph_prologue(iter, s, 0, 0))
                 return TRACE_TYPE_PARTIAL_LINE;
@@ -941,8 +990,33 @@ print_graph_comment(struct trace_seq *s,  struct trace_entry *ent,
 enum print_line_t
 print_graph_function(struct trace_iterator *iter)
 {
+        struct ftrace_graph_ent_entry *field;
+        struct fgraph_data *data = iter->private;
         struct trace_entry *entry = iter->ent;
         struct trace_seq *s = &iter->seq;
+        int cpu = iter->cpu;
+        int ret;
+
+        if (data && per_cpu_ptr(data->cpu_data, cpu)->ignore) {
+                per_cpu_ptr(data->cpu_data, cpu)->ignore = 0;
+                return TRACE_TYPE_HANDLED;
+        }
+
+        /*
+         * If the last output failed, there's a possibility we need
+         * to print out the missing entry which would never go out.
+         */
+        if (data && data->failed) {
+                field = &data->ent;
+                iter->cpu = data->cpu;
+                ret = print_graph_entry(field, s, iter);
+                if (ret == TRACE_TYPE_HANDLED && iter->cpu != cpu) {
+                        per_cpu_ptr(data->cpu_data, iter->cpu)->ignore = 1;
+                        ret = TRACE_TYPE_NO_CONSUME;
+                }
+                iter->cpu = cpu;
+                return ret;
+        }
 
         switch (entry->type) {
         case TRACE_GRAPH_ENT: {
@@ -952,7 +1026,7 @@ print_graph_function(struct trace_iterator *iter)
                  * sizeof(struct ftrace_graph_ent_entry) is very small,
                  * it can be safely saved at the stack.
                  */
-                struct ftrace_graph_ent_entry *field, saved;
+                struct ftrace_graph_ent_entry saved;
                 trace_assign_type(field, entry);
                 saved = *field;
                 return print_graph_entry(&saved, s, iter);
@@ -1030,31 +1104,54 @@ static void print_graph_headers(struct seq_file *s)
 static void graph_trace_open(struct trace_iterator *iter)
 {
         /* pid and depth on the last trace processed */
-        struct fgraph_data *data = alloc_percpu(struct fgraph_data);
+        struct fgraph_data *data;
         int cpu;
 
+        iter->private = NULL;
+
+        data = kzalloc(sizeof(*data), GFP_KERNEL);
         if (!data)
-                pr_warning("function graph tracer: not enough memory\n");
-        else
-                for_each_possible_cpu(cpu) {
-                        pid_t *pid = &(per_cpu_ptr(data, cpu)->last_pid);
-                        int *depth = &(per_cpu_ptr(data, cpu)->depth);
-                        *pid = -1;
-                        *depth = 0;
-                }
+                goto out_err;
+
+        data->cpu_data = alloc_percpu(struct fgraph_cpu_data);
+        if (!data->cpu_data)
+                goto out_err_free;
+
+        for_each_possible_cpu(cpu) {
+                pid_t *pid = &(per_cpu_ptr(data->cpu_data, cpu)->last_pid);
+                int *depth = &(per_cpu_ptr(data->cpu_data, cpu)->depth);
+                int *ignore = &(per_cpu_ptr(data->cpu_data, cpu)->ignore);
+                *pid = -1;
+                *depth = 0;
+                *ignore = 0;
+        }
 
         iter->private = data;
+
+        return;
+
+ out_err_free:
+        kfree(data);
+ out_err:
+        pr_warning("function graph tracer: not enough memory\n");
 }
 
 static void graph_trace_close(struct trace_iterator *iter)
 {
-        free_percpu(iter->private);
+        struct fgraph_data *data = iter->private;
+
+        if (data) {
+                free_percpu(data->cpu_data);
+                kfree(data);
+        }
 }
 
 static struct tracer graph_trace __read_mostly = {
         .name           = "function_graph",
         .open           = graph_trace_open,
+        .pipe_open      = graph_trace_open,
         .close          = graph_trace_close,
+        .pipe_close     = graph_trace_close,
         .wait_pipe      = poll_wait_pipe,
         .init           = graph_trace_init,
         .reset          = graph_trace_reset,