2017-07-06 23:00:41

by Joel Fernandes

Subject: [PATCH 1/3] tracing: Treat recording comm for idle task as a success

Currently we stop recording comm for non-idle tasks when switching from/to idle
task since we treat that as a record failure. Fix that by treat recording of
comm for idle task as a success.

Cc: [email protected]
Cc: Steven Rostedt <[email protected]>
Cc: Ingo Molnar <[email protected]>
Reported-by: Michael Sartain <[email protected]>
Signed-off-by: Joel Fernandes <[email protected]>
---
kernel/trace/trace.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index c579dea4a0eb..7a0c493723a9 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -1916,7 +1916,11 @@ static int trace_save_cmdline(struct task_struct *tsk)
{
unsigned pid, idx;

- if (!tsk->pid || unlikely(tsk->pid > PID_MAX_DEFAULT))
+ /* treat recording of idle task as a success */
+ if (!tsk->pid)
+ return 1;
+
+ if (unlikely(tsk->pid > PID_MAX_DEFAULT))
return 0;

/*
--
2.13.2.725.g09c95d1e9-goog

2017-07-06 23:00:43

by Joel Fernandes

Subject: [PATCH 2/3] tracing: Treat recording tgid for idle task as a success

Currently we stop recording tgid for non-idle tasks when switching from/to idle
task since we treat that as a record failure. Fix that by treat recording of
tgid for idle task as a success.

Cc: [email protected]
Cc: Steven Rostedt <[email protected]>
Cc: Ingo Molnar <[email protected]>
Reported-by: Michael Sartain <[email protected]>
Signed-off-by: Joel Fernandes <[email protected]>
---
kernel/trace/trace.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 7a0c493723a9..363924f90e2f 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -2006,7 +2006,11 @@ int trace_find_tgid(int pid)

static int trace_save_tgid(struct task_struct *tsk)
{
- if (unlikely(!tgid_map || !tsk->pid || tsk->pid > PID_MAX_DEFAULT))
+ /* treat recording of idle task as a success */
+ if (!tsk->pid)
+ return 1;
+
+ if (unlikely(!tgid_map || tsk->pid > PID_MAX_DEFAULT))
return 0;

tgid_map[tsk->pid] = tsk->tgid;
--
2.13.2.725.g09c95d1e9-goog

2017-07-06 23:00:48

by Joel Fernandes

Subject: [PATCH 3/3] tracing: Attempt to record other information even if some fail

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.

Cc: [email protected]
Cc: Steven Rostedt <[email protected]>
Cc: Ingo Molnar <[email protected]>
Signed-off-by: Joel Fernandes <[email protected]>
---
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 363924f90e2f..8a44e9cb2594 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);
--
2.13.2.725.g09c95d1e9-goog