Hi Sasha,
On Sun, Feb 17, 2019 at 09:06:36PM -0500, Sasha Levin wrote:
> On Fri, Feb 15, 2019 at 12:26:35PM +0000, Chris Redpath wrote:
> > Hi Greg et al.
> >
> > A user of android-4.14 has pointed the following missing commit out.
> >
> > Commit 3054426dc68e ("sched, trace: Fix prev_state output in sched_switch tracepoint") was put into linux-4.20 around rc5 to fix an issue in a tracepoint. According to the patch itself, the broken commit was 3f5fe9fef5b2 ("sched/debug: Fix task state recording/printout") which was merged at what looks like 4.15-rc2. The broken commit was also picked for 4.14.64 as 13f12749af15 ("sched/debug: Fix task state recording/printout"). The fix (3054426dc68e) was pulled into 4.19. but was not called out as needing to go back to 4.14.
> >
> > Is it possible to pick 3054426dc68e ("sched, trace: Fix prev_state output in sched_switch tracepoint") for the next stable 4.14 release? If not I can do a backport for android-4.14, just let me know.
>
> It wasn't backported because it didn't apply cleanly, since 4.4's
> backport of 3f5fe9fef5b2 differs from Linus's tree.
>
> The backport for that commit was done by Sudip (Cc'ed). I'll be happy to
> take a backport of 3054426dc68e if someone sense one my way.
Happy to do a backport for 4.14-stable. :)
It did not apply before as the function was only renamed by:
1d48b080bcce ("sched/debug: Rename task-state printing helpers")
There was no other functionality change.
--
Regards
Sudip
>From f8c12fb36c1164fbd1ffaabd9898dfb2af1ee28a Mon Sep 17 00:00:00 2001
From: Pavankumar Kondeti <pkondeti@xxxxxxxxxxxxxx>
Date: Tue, 30 Oct 2018 12:24:33 +0530
Subject: [PATCH] sched, trace: Fix prev_state output in sched_switch tracepoint
commit 3054426dc68e5d63aa6a6e9b91ac4ec78e3f3805 upstream
commit 3f5fe9fef5b2 ("sched/debug: Fix task state recording/printout")
tried to fix the problem introduced by a previous commit efb40f588b43
("sched/tracing: Fix trace_sched_switch task-state printing"). However
the prev_state output in sched_switch is still broken.
task_state_index() uses fls() which considers the LSB as 1. Left
shifting 1 by this value gives an incorrect mapping to the task state.
Fix this by decrementing the value returned by __get_task_state()
before shifting.
Link: http://lkml.kernel.org/r/1540882473-1103-1-git-send-email-pkondeti@xxxxxxxxxxxxxx
Cc: stable@xxxxxxxxxxxxxxx
Fixes: 3f5fe9fef5b2 ("sched/debug: Fix task state recording/printout")
Signed-off-by: Pavankumar Kondeti <pkondeti@xxxxxxxxxxxxxx>
Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
Signed-off-by: Sudip Mukherjee <sudipm.mukherjee@xxxxxxxxx>
---
include/trace/events/sched.h | 12 +++++++++++-
1 file changed, 11 insertions(+), 1 deletion(-)
diff --git a/include/trace/events/sched.h b/include/trace/events/sched.h
index 0812cd5408c9..6e692a52936c 100644
--- a/include/trace/events/sched.h
+++ b/include/trace/events/sched.h
@@ -107,6 +107,8 @@ DEFINE_EVENT(sched_wakeup_template, sched_wakeup_new,
#ifdef CREATE_TRACE_POINTS
static inline long __trace_sched_switch_state(bool preempt, struct task_struct *p)
{
+ unsigned int state;
+
#ifdef CONFIG_SCHED_DEBUG
BUG_ON(p != current);
#endif /* CONFIG_SCHED_DEBUG */
@@ -118,7 +120,15 @@ static inline long __trace_sched_switch_state(bool preempt, struct task_struct *
if (preempt)
return TASK_REPORT_MAX;
- return 1 << __get_task_state(p);
+ /*
+ * task_state_index() uses fls() and returns a value from 0-8 range.
+ * Decrement it by 1 (except TASK_RUNNING state i.e 0) before using
+ * it for left shift operation to get the correct task->state
+ * mapping.
+ */
+ state = __get_task_state(p);
+
+ return state ? (1 << (state - 1)) : state;
}
#endif /* CREATE_TRACE_POINTS */
--
2.11.0
