tracing/ftrace: change the type of the print_line callback

We need a kind of disambiguation when a print_line callback
returns 0.

_There is not enough space to print all the entry.
 Please flush the seq and retry.
_I can't handle this type of entry

This patch changes the type of this callback for better information.

Also some changes have been made in this V2.

_ Only relay to default functions after the print_line callback fails.
_ This patch doesn't fix the issue with the broken pipe (see patch 2/4 for that)

Some things are still in discussion:

_ Find better names for the enum print_line_t values
_ Change the type of print_trace_line into boolean.

Patches to change that can be sent later.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: Pekka Paalanen <pq@iki.fi>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

2 files changed, 50 insertions, 37 deletions

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index ed9e47c1881..b38a4bb4054 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -1250,7 +1250,7 @@ void trace_seq_print_cont(struct trace_seq *s, struct trace_iterator *iter)
                 trace_seq_putc(s, '\n');
 }
 
-static int
+static enum print_line_t
 print_lat_fmt(struct trace_iterator *iter, unsigned int trace_idx, int cpu)
 {
         struct trace_seq *s = &iter->seq;
@@ -1267,7 +1267,7 @@ print_lat_fmt(struct trace_iterator *iter, unsigned int trace_idx, int cpu)
         unsigned state;
 
         if (entry->type == TRACE_CONT)
-                return 1;
+                return TRACE_TYPE_HANDLED;
 
         next_entry = find_next_entry(iter, NULL, &next_ts);
         if (!next_entry)
@@ -1357,10 +1357,10 @@ print_lat_fmt(struct trace_iterator *iter, unsigned int trace_idx, int cpu)
         default:
                 trace_seq_printf(s, "Unknown type %d\n", entry->type);
         }
-        return 1;
+        return TRACE_TYPE_HANDLED;
 }
 
-static int print_trace_fmt(struct trace_iterator *iter)
+static enum print_line_t print_trace_fmt(struct trace_iterator *iter)
 {
         struct trace_seq *s = &iter->seq;
         unsigned long sym_flags = (trace_flags & TRACE_ITER_SYM_MASK);
@@ -1376,7 +1376,7 @@ static int print_trace_fmt(struct trace_iterator *iter)
         entry = iter->ent;
 
         if (entry->type == TRACE_CONT)
-                return 1;
+                return TRACE_TYPE_HANDLED;
 
         comm = trace_find_cmdline(iter->ent->pid);
 
@@ -1386,13 +1386,13 @@ static int print_trace_fmt(struct trace_iterator *iter)
 
         ret = trace_seq_printf(s, "%16s-%-5d ", comm, entry->pid);
         if (!ret)
-                return 0;
+                return TRACE_TYPE_PARTIAL_LINE;
         ret = trace_seq_printf(s, "[%03d] ", iter->cpu);
         if (!ret)
-                return 0;
+                return TRACE_TYPE_PARTIAL_LINE;
         ret = trace_seq_printf(s, "%5lu.%06lu: ", secs, usec_rem);
         if (!ret)
-                return 0;
+                return TRACE_TYPE_PARTIAL_LINE;
 
         switch (entry->type) {
         case TRACE_FN: {
@@ -1400,12 +1400,12 @@ static int print_trace_fmt(struct trace_iterator *iter)
 
                 ret = seq_print_ip_sym(s, field->ip, sym_flags);
                 if (!ret)
-                        return 0;
+                        return TRACE_TYPE_PARTIAL_LINE;
                 if ((sym_flags & TRACE_ITER_PRINT_PARENT) &&
                                                 field->parent_ip) {
                         ret = trace_seq_printf(s, " <-");
                         if (!ret)
-                                return 0;
+                                return TRACE_TYPE_PARTIAL_LINE;
                         if (kretprobed(field->parent_ip))
                                 ret = trace_seq_puts(s, KRETPROBE_MSG);
                         else
@@ -1413,11 +1413,11 @@ static int print_trace_fmt(struct trace_iterator *iter)
                                                        field->parent_ip,
                                                        sym_flags);
                         if (!ret)
-                                return 0;
+                                return TRACE_TYPE_PARTIAL_LINE;
                 }
                 ret = trace_seq_printf(s, "\n");
                 if (!ret)
-                        return 0;
+                        return TRACE_TYPE_PARTIAL_LINE;
                 break;
         }
         case TRACE_CTX:
@@ -1439,7 +1439,7 @@ static int print_trace_fmt(struct trace_iterator *iter)
                                        field->next_prio,
                                        T);
                 if (!ret)
-                        return 0;
+                        return TRACE_TYPE_PARTIAL_LINE;
                 break;
         }
         case TRACE_SPECIAL: {
@@ -1450,7 +1450,7 @@ static int print_trace_fmt(struct trace_iterator *iter)
                                  field->arg2,
                                  field->arg3);
                 if (!ret)
-                        return 0;
+                        return TRACE_TYPE_PARTIAL_LINE;
                 break;
         }
         case TRACE_STACK: {
@@ -1460,16 +1460,16 @@ static int print_trace_fmt(struct trace_iterator *iter)
                         if (i) {
                                 ret = trace_seq_puts(s, " <= ");
                                 if (!ret)
-                                        return 0;
+                                        return TRACE_TYPE_PARTIAL_LINE;
                         }
                         ret = seq_print_ip_sym(s, field->caller[i],
                                                sym_flags);
                         if (!ret)
-                                return 0;
+                                return TRACE_TYPE_PARTIAL_LINE;
                 }
                 ret = trace_seq_puts(s, "\n");
                 if (!ret)
-                        return 0;
+                        return TRACE_TYPE_PARTIAL_LINE;
                 break;
         }
         case TRACE_PRINT: {
@@ -1482,10 +1482,10 @@ static int print_trace_fmt(struct trace_iterator *iter)
                 break;
         }
         }
-        return 1;
+        return TRACE_TYPE_HANDLED;
 }
 
-static int print_raw_fmt(struct trace_iterator *iter)
+static enum print_line_t print_raw_fmt(struct trace_iterator *iter)
 {
         struct trace_seq *s = &iter->seq;
         struct trace_entry *entry;
@@ -1495,12 +1495,12 @@ static int print_raw_fmt(struct trace_iterator *iter)
         entry = iter->ent;
 
         if (entry->type == TRACE_CONT)
-                return 1;
+                return TRACE_TYPE_HANDLED;
 
         ret = trace_seq_printf(s, "%d %d %llu ",
                 entry->pid, iter->cpu, iter->ts);
         if (!ret)
-                return 0;
+                return TRACE_TYPE_PARTIAL_LINE;
 
         switch (entry->type) {
         case TRACE_FN: {
@@ -1510,7 +1510,7 @@ static int print_raw_fmt(struct trace_iterator *iter)
                                         field->ip,
                                         field->parent_ip);
                 if (!ret)
-                        return 0;
+                        return TRACE_TYPE_PARTIAL_LINE;
                 break;
         }
         case TRACE_CTX:
@@ -1533,7 +1533,7 @@ static int print_raw_fmt(struct trace_iterator *iter)
                                        field->next_prio,
                                        T);
                 if (!ret)
-                        return 0;
+                        return TRACE_TYPE_PARTIAL_LINE;
                 break;
         }
         case TRACE_SPECIAL:
@@ -1545,7 +1545,7 @@ static int print_raw_fmt(struct trace_iterator *iter)
                                  field->arg2,
                                  field->arg3);
                 if (!ret)
-                        return 0;
+                        return TRACE_TYPE_PARTIAL_LINE;
                 break;
         }
         case TRACE_PRINT: {
@@ -1557,7 +1557,7 @@ static int print_raw_fmt(struct trace_iterator *iter)
                 break;
         }
         }
-        return 1;
+        return TRACE_TYPE_HANDLED;
 }
 
 #define SEQ_PUT_FIELD_RET(s, x)                         \
@@ -1572,7 +1572,7 @@ do {							\
                 return 0;                               \
 } while (0)
 
-static int print_hex_fmt(struct trace_iterator *iter)
+static enum print_line_t print_hex_fmt(struct trace_iterator *iter)
 {
         struct trace_seq *s = &iter->seq;
         unsigned char newline = '\n';
@@ -1582,7 +1582,7 @@ static int print_hex_fmt(struct trace_iterator *iter)
         entry = iter->ent;
 
         if (entry->type == TRACE_CONT)
-                return 1;
+                return TRACE_TYPE_HANDLED;
 
         SEQ_PUT_HEX_FIELD_RET(s, entry->pid);
         SEQ_PUT_HEX_FIELD_RET(s, iter->cpu);
@@ -1628,10 +1628,10 @@ static int print_hex_fmt(struct trace_iterator *iter)
         }
         SEQ_PUT_FIELD_RET(s, newline);
 
-        return 1;
+        return TRACE_TYPE_HANDLED;
 }
 
-static int print_bin_fmt(struct trace_iterator *iter)
+static enum print_line_t print_bin_fmt(struct trace_iterator *iter)
 {
         struct trace_seq *s = &iter->seq;
         struct trace_entry *entry;
@@ -1639,7 +1639,7 @@ static int print_bin_fmt(struct trace_iterator *iter)
         entry = iter->ent;
 
         if (entry->type == TRACE_CONT)
-                return 1;
+                return TRACE_TYPE_HANDLED;
 
         SEQ_PUT_FIELD_RET(s, entry->pid);
         SEQ_PUT_FIELD_RET(s, iter->cpu);
@@ -1686,13 +1686,18 @@ static int trace_empty(struct trace_iterator *iter)
                 if (!ring_buffer_iter_empty(iter->buffer_iter[cpu]))
                         return 0;
         }
-        return 1;
+        return TRACE_TYPE_HANDLED;
 }
 
-static int print_trace_line(struct trace_iterator *iter)
+static enum print_line_t print_trace_line(struct trace_iterator *iter)
 {
-        if (iter->trace && iter->trace->print_line)
-                return iter->trace->print_line(iter);
+        enum print_line_t ret;
+
+        if (iter->trace && iter->trace->print_line) {
+                ret = iter->trace->print_line(iter);
+                if (ret != TRACE_TYPE_UNHANDLED)
+                        return ret;
+        }
 
         if (trace_flags & TRACE_ITER_BIN)
                 return print_bin_fmt(iter);
@@ -2525,11 +2530,11 @@ tracing_read_pipe(struct file *filp, char __user *ubuf,
         ring_buffer_lock(iter->tr->buffer, &flags);
 
         while (find_next_entry_inc(iter) != NULL) {
-                int ret;
+                enum print_line_t ret;
                 int len = iter->seq.len;
 
                 ret = print_trace_line(iter);
-                if (!ret) {
+                if (ret == TRACE_TYPE_PARTIAL_LINE) {
                         /* don't print partial lines */
                         iter->seq.len = len;
                         break;
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index e541a6b7e31..a921ba5d292 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -177,6 +177,14 @@ struct trace_array {
         struct trace_array_cpu  *data[NR_CPUS];
 };
 
+
+/* Return values for print_line callback */
+enum print_line_t {
+        TRACE_TYPE_PARTIAL_LINE = 0,    /* Retry after flushing the seq */
+        TRACE_TYPE_HANDLED      = 1,
+        TRACE_TYPE_UNHANDLED    = 2     /* Relay to other output functions */
+};
+
 /*
  * A specific tracer, represented by methods that operate on a trace array:
  */
@@ -197,7 +205,7 @@ struct tracer {
         int                     (*selftest)(struct tracer *trace,
                                             struct trace_array *tr);
 #endif
-        int                     (*print_line)(struct trace_iterator *iter);
+        enum print_line_t       (*print_line)(struct trace_iterator *iter);
         struct tracer           *next;
         int                     print_max;
 };