linux-kernel - [PATCH v2] seqlock: mark raw_read_seqcount and read_seqcount_retry as __always

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Date:   Tue, 11 Jun 2019 17:47:51 +0200
From:   Anders Roxell <anders.roxell@...aro.org>
To:     peterz@...radead.org, mingo@...hat.com, will.deacon@....com
Cc:     tglx@...utronix.de, linux-kernel@...r.kernel.org,
        Anders Roxell <anders.roxell@...aro.org>
Subject: [PATCH v2] seqlock: mark raw_read_seqcount and read_seqcount_retry as __always_inline

With the function graph tracer, each traced function calls sched_clock()
to take a timestamp. As sched_clock() uses
raw_read_seqcount()/read_seqcount_retry(), we must ensure that these
do not in turn trigger the graph tracer.
Both functions is marked as inline. However, if CONFIG_OPTIMIZE_INLINING
is set that may make the two functions tracable which they shouldn't.

Rework so that functions raw_read_seqcount and read_seqcount_retry are
marked with __always_inline so they will be inlined even if
CONFIG_OPTIMIZE_INLINING is turned on.

Acked-by: Will Deacon <will.deacon@....com>
Signed-off-by: Anders Roxell <anders.roxell@...aro.org>
---
 include/linux/seqlock.h | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/include/linux/seqlock.h b/include/linux/seqlock.h
index bcf4cf26b8c8..1b18e3df186e 100644
--- a/include/linux/seqlock.h
+++ b/include/linux/seqlock.h
@@ -127,7 +127,7 @@ static inline unsigned __read_seqcount_begin(const seqcount_t *s)
  * seqcount without any lockdep checking and without checking or
  * masking the LSB. Calling code is responsible for handling that.
  */
-static inline unsigned raw_read_seqcount(const seqcount_t *s)
+static __always_inline unsigned raw_read_seqcount(const seqcount_t *s)
 {
 	unsigned ret = READ_ONCE(s->sequence);
 	smp_rmb();
@@ -215,7 +215,8 @@ static inline int __read_seqcount_retry(const seqcount_t *s, unsigned start)
  * If the critical section was invalid, it must be ignored (and typically
  * retried).
  */
-static inline int read_seqcount_retry(const seqcount_t *s, unsigned start)
+static
+__always_inline int read_seqcount_retry(const seqcount_t *s, unsigned start)
 {
 	smp_rmb();
 	return __read_seqcount_retry(s, start);
-- 
2.20.1