[PATCH 5.15 024/177] s390/entry: fix duplicate tracking of irq nesting level

Greg Kroah-Hartman
2021-12-20T15:05:40Z

From: Sven Schnelle <svens@linux.ibm.com>

commit c9b12b59e2ea4c3c7cedec7efb071b649652f3a9 upstream.

In the current code, when exiting from idle, rcu_irq_enter() is
called twice during irq entry:

irq_entry_enter()-> rcu_irq_enter()
irq_enter() -> rcu_irq_enter()

This may lead to wrong results from rcu_is_cpu_rrupt_from_idle()
because of a wrong dynticks nmi nesting count. Fix this by only
calling irq_enter_rcu().

Cc: <stable@vger.kernel.org> # 5.12+
Reported-by: Mark Rutland <mark.rutland@arm.com>
Fixes: 56e62a737028 ("s390: convert to generic entry")
Signed-off-by: Sven Schnelle <svens@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/s390/kernel/irq.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)

--- a/arch/s390/kernel/irq.c
+++ b/arch/s390/kernel/irq.c
@@ -138,7 +138,7 @@ void noinstr do_io_irq(struct pt_regs *r
struct pt_regs *old_regs = set_irq_regs(regs);
int from_idle;

- irq_enter();
+ irq_enter_rcu();

if (user_mode(regs))
update_timer_sys();
@@ -155,7 +155,8 @@ void noinstr do_io_irq(struct pt_regs *r
do_irq_async(regs, IO_INTERRUPT);
} while (MACHINE_IS_LPAR && irq_pending(regs));

- irq_exit();
+ irq_exit_rcu();
+
set_irq_regs(old_regs);
irqentry_exit(regs, state);

@@ -169,7 +170,7 @@ void noinstr do_ext_irq(struct pt_regs *
struct pt_regs *old_regs = set_irq_regs(regs);
int from_idle;

- irq_enter();
+ irq_enter_rcu();

if (user_mode(regs))
update_timer_sys();
@@ -184,7 +185,7 @@ void noinstr do_ext_irq(struct pt_regs *

do_irq_async(regs, EXT_INTERRUPT);

- irq_exit();
+ irq_exit_rcu();
set_irq_regs(old_regs);
irqentry_exit(regs, state);