From: Mark Rutland <mark.rutland@arm.com>
To: linux-kernel@vger.kernel.org
Cc: benh@kernel.crashing.org, boqun.feng@gmail.com, bp@alien8.de,
catalin.marinas@arm.com, dvyukov@google.com, elver@google.com,
ink@jurassic.park.msu.ru, jonas@southpole.se,
juri.lelli@redhat.com, linux@armlinux.org.uk, luto@kernel.org,
mark.rutland@arm.com, mattst88@gmail.com, mingo@redhat.com,
monstr@monstr.eu, mpe@ellerman.id.au, paulmck@kernel.org,
paulus@samba.org, peterz@infradead.org, rth@twiddle.net,
shorne@gmail.com, stefan.kristiansson@saunalahti.fi,
tglx@linutronix.de, vincent.guittot@linaro.org, will@kernel.org
Subject: [RFC PATCH 01/10] thread_info: add helpers to snapshot thread flags
Date: Wed, 9 Jun 2021 13:19:52 +0100 [thread overview]
Message-ID: <20210609122001.18277-2-mark.rutland@arm.com> (raw)
In-Reply-To: <20210609122001.18277-1-mark.rutland@arm.com>
We have common helpers to manipulate individual thread flags, but where
code wants to check several flags at once, it must open code reading
current_thread_info()->flags and operating on a snapshot.
As some flags can be set remotely it's necessary to use READ_ONCE() to
get a consistent snapshot even when IRQs are disabled, but some code
forgets to do this. Generally this is unlike to cause a problem in
practice, but it is somewhat unsound, and KCSAN will legitimately warn
that there is a data race.
To make it easier to do the right thing, and to highlight that
concurrent modification is possible, let's add a new helpers to snapshot
the flags, which should be used in preference to plain reads.
Subsequent patches will move existing code to use the new helpers.
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Marco Elver <elver@google.com>
Cc: Paul E. McKenney <paulmck@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Will Deacon <will@kernel.org>
---
include/linux/thread_info.h | 10 ++++++++++
1 file changed, 10 insertions(+)
diff --git a/include/linux/thread_info.h b/include/linux/thread_info.h
index 157762db9d4b..f3769842046d 100644
--- a/include/linux/thread_info.h
+++ b/include/linux/thread_info.h
@@ -117,6 +117,11 @@ static inline int test_ti_thread_flag(struct thread_info *ti, int flag)
return test_bit(flag, (unsigned long *)&ti->flags);
}
+static inline unsigned long read_ti_thread_flags(struct thread_info *ti)
+{
+ return READ_ONCE(ti->flags);
+}
+
#define set_thread_flag(flag) \
set_ti_thread_flag(current_thread_info(), flag)
#define clear_thread_flag(flag) \
@@ -129,6 +134,11 @@ static inline int test_ti_thread_flag(struct thread_info *ti, int flag)
test_and_clear_ti_thread_flag(current_thread_info(), flag)
#define test_thread_flag(flag) \
test_ti_thread_flag(current_thread_info(), flag)
+#define read_thread_flags() \
+ read_ti_thread_flags(current_thread_info())
+
+#define read_task_thread_flags(t) \
+ read_ti_thread_flags(task_thread_info(t))
#ifdef CONFIG_GENERIC_ENTRY
#define set_syscall_work(fl) \
--
2.11.0
next prev parent reply other threads:[~2021-06-09 12:20 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-09 12:19 [RFC PATCH 00/10] thread_info: use helpers to snapshot thread flags Mark Rutland
2021-06-09 12:19 ` Mark Rutland [this message]
2021-06-10 9:01 ` [RFC PATCH 01/10] thread_info: add " Marco Elver
2021-06-11 9:17 ` Mark Rutland
2021-06-19 22:28 ` Thomas Gleixner
2021-06-21 8:29 ` Mark Rutland
2021-06-09 12:19 ` [RFC PATCH 02/10] entry: " Mark Rutland
2021-06-09 12:19 ` [RFC PATCH 03/10] sched: " Mark Rutland
2021-06-09 12:19 ` [RFC PATCH 04/10] alpha: " Mark Rutland
2021-06-09 12:19 ` [RFC PATCH 05/10] arm: " Mark Rutland
2021-06-09 12:19 ` [RFC PATCH 06/10] arm64: read " Mark Rutland
2021-06-16 22:07 ` kernel test robot
2021-06-09 12:19 ` [RFC PATCH 07/10] microblaze: snapshot " Mark Rutland
2021-06-09 12:19 ` [RFC PATCH 08/10] openrisc: " Mark Rutland
2021-06-10 19:14 ` Stafford Horne
2021-06-09 12:20 ` [RFC PATCH 09/10] powerpc: " Mark Rutland
2021-06-15 13:18 ` Michael Ellerman
2021-06-21 8:46 ` Mark Rutland
2021-06-09 12:20 ` [RFC PATCH 10/10] x86: " Mark Rutland
2021-06-19 22:30 ` Thomas Gleixner
2021-06-21 8:35 ` Mark Rutland
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