[for-next][PATCH 4/4] tracing: Attempt to record other information even if some fail

[Steven Rostedt]

From: Joel Fernandes <joelaf@xxxxxxxxxx>

In recent patches where we record comm and tgid at the same time, we skip
continuing to record if any fail. Fix that by trying to record as many things
as we can even if some couldn't be recorded. If any information isn't recorded,
then we don't set trace_taskinfo_save as before.

Link: http://lkml.kernel.org/r/20170706230023.17942-3-joelaf@xxxxxxxxxx

Cc: kernel-team@xxxxxxxxxxx
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Signed-off-by: Joel Fernandes <joelaf@xxxxxxxxxx>
Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
---
 kernel/trace/trace.c | 32 ++++++++++++++++++++++++--------
 1 file changed, 24 insertions(+), 8 deletions(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index aee11e3a394f..92af8fd1429b 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -2037,11 +2037,20 @@ static bool tracing_record_taskinfo_skip(int flags)
  */
 void tracing_record_taskinfo(struct task_struct *task, int flags)
 {
+	bool done;
+
 	if (tracing_record_taskinfo_skip(flags))
 		return;
-	if ((flags & TRACE_RECORD_CMDLINE) && !trace_save_cmdline(task))
-		return;
-	if ((flags & TRACE_RECORD_TGID) && !trace_save_tgid(task))
+
+	/*
+	 * Record as much task information as possible. If some fail, continue
+	 * to try to record the others.
+	 */
+	done = !(flags & TRACE_RECORD_CMDLINE) || trace_save_cmdline(task);
+	done &= !(flags & TRACE_RECORD_TGID) || trace_save_tgid(task);
+
+	/* If recording any information failed, retry again soon. */
+	if (!done)
 		return;
 
 	__this_cpu_write(trace_taskinfo_save, false);
@@ -2058,15 +2067,22 @@ void tracing_record_taskinfo(struct task_struct *task, int flags)
 void tracing_record_taskinfo_sched_switch(struct task_struct *prev,
 					  struct task_struct *next, int flags)
 {
+	bool done;
+
 	if (tracing_record_taskinfo_skip(flags))
 		return;
 
-	if ((flags & TRACE_RECORD_CMDLINE) &&
-	    (!trace_save_cmdline(prev) || !trace_save_cmdline(next)))
-		return;
+	/*
+	 * Record as much task information as possible. If some fail, continue
+	 * to try to record the others.
+	 */
+	done  = !(flags & TRACE_RECORD_CMDLINE) || trace_save_cmdline(prev);
+	done &= !(flags & TRACE_RECORD_CMDLINE) || trace_save_cmdline(next);
+	done &= !(flags & TRACE_RECORD_TGID) || trace_save_tgid(prev);
+	done &= !(flags & TRACE_RECORD_TGID) || trace_save_tgid(next);
 
-	if ((flags & TRACE_RECORD_TGID) &&
-	    (!trace_save_tgid(prev) || !trace_save_tgid(next)))
+	/* If recording any information failed, retry again soon. */
+	if (!done)
 		return;
 
 	__this_cpu_write(trace_taskinfo_save, false);
-- 
2.10.2