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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: [PATCH v4 02/10] entry: snapshot thread flags
Date: Tue,  3 Aug 2021 10:54:20 +0100	[thread overview]
Message-ID: <20210803095428.17009-3-mark.rutland@arm.com> (raw)
In-Reply-To: <20210803095428.17009-1-mark.rutland@arm.com>

Some thread flags can be set remotely, and so even when IRQs are
disabled, the flags can change under our feet. Generally this is
unlikely to cause a problem in practice, but it is somewhat unsound, and
KCSAN will legitimately warn that there is a data race.

To avoid such issues, a snapshot of the flags has to be taken prior to
using them. Some places already use READ_ONCE() for that, others do not.

Convert them all to the new flag accessor helpers.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
---
 include/linux/entry-kvm.h | 2 +-
 kernel/entry/common.c     | 4 ++--
 kernel/entry/kvm.c        | 4 ++--
 3 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/include/linux/entry-kvm.h b/include/linux/entry-kvm.h
index 136b8d97d8c0..2bd3b1f10fd1 100644
--- a/include/linux/entry-kvm.h
+++ b/include/linux/entry-kvm.h
@@ -71,7 +71,7 @@ static inline void xfer_to_guest_mode_prepare(void)
  */
 static inline bool __xfer_to_guest_mode_work_pending(void)
 {
-	unsigned long ti_work = READ_ONCE(current_thread_info()->flags);
+	unsigned long ti_work = read_thread_flags();
 
 	return !!(ti_work & XFER_TO_GUEST_MODE_WORK);
 }
diff --git a/kernel/entry/common.c b/kernel/entry/common.c
index bf16395b9e13..49bd64c43fe9 100644
--- a/kernel/entry/common.c
+++ b/kernel/entry/common.c
@@ -189,7 +189,7 @@ static unsigned long exit_to_user_mode_loop(struct pt_regs *regs,
 		/* Check if any of the above work has queued a deferred wakeup */
 		tick_nohz_user_enter_prepare();
 
-		ti_work = READ_ONCE(current_thread_info()->flags);
+		ti_work = read_thread_flags();
 	}
 
 	/* Return the latest work state for arch_exit_to_user_mode() */
@@ -198,7 +198,7 @@ static unsigned long exit_to_user_mode_loop(struct pt_regs *regs,
 
 static void exit_to_user_mode_prepare(struct pt_regs *regs)
 {
-	unsigned long ti_work = READ_ONCE(current_thread_info()->flags);
+	unsigned long ti_work = read_thread_flags();
 
 	lockdep_assert_irqs_disabled();
 
diff --git a/kernel/entry/kvm.c b/kernel/entry/kvm.c
index 49972ee99aff..96d476e06c77 100644
--- a/kernel/entry/kvm.c
+++ b/kernel/entry/kvm.c
@@ -26,7 +26,7 @@ static int xfer_to_guest_mode_work(struct kvm_vcpu *vcpu, unsigned long ti_work)
 		if (ret)
 			return ret;
 
-		ti_work = READ_ONCE(current_thread_info()->flags);
+		ti_work = read_thread_flags();
 	} while (ti_work & XFER_TO_GUEST_MODE_WORK || need_resched());
 	return 0;
 }
@@ -43,7 +43,7 @@ int xfer_to_guest_mode_handle_work(struct kvm_vcpu *vcpu)
 	 * disabled in the inner loop before going into guest mode. No need
 	 * to disable interrupts here.
 	 */
-	ti_work = READ_ONCE(current_thread_info()->flags);
+	ti_work = read_thread_flags();
 	if (!(ti_work & XFER_TO_GUEST_MODE_WORK))
 		return 0;
 
-- 
2.11.0


  parent reply	other threads:[~2021-08-03  9:55 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-03  9:54 [PATCH v4 00/10] thread_info: use helpers to " Mark Rutland
2021-08-03  9:54 ` [PATCH v4 01/10] thread_info: add " Mark Rutland
2021-08-03  9:54 ` Mark Rutland [this message]
2021-08-03  9:54 ` [PATCH v4 03/10] sched: " Mark Rutland
2021-08-03  9:54 ` [PATCH v4 04/10] alpha: " Mark Rutland
2021-08-03  9:54 ` [PATCH v4 05/10] arm: " Mark Rutland
2021-08-03  9:54 ` [PATCH v4 06/10] arm64: " Mark Rutland
2021-08-03  9:54 ` [PATCH v4 07/10] microblaze: " Mark Rutland
2021-08-25  9:03   ` Michal Simek
2021-08-03  9:54 ` [PATCH v4 08/10] openrisc: " Mark Rutland
2021-08-03  9:54 ` [PATCH v4 09/10] powerpc: " Mark Rutland
2021-08-03  9:54 ` [PATCH v4 10/10] x86: " Mark Rutland
2021-08-03 16:01 ` [PATCH v4 00/10] thread_info: use helpers to " Paul E. McKenney

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