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Message-ID: <159851486889.20229.2481874013860233958.tip-bot2@tip-bot2>
Date: Thu, 27 Aug 2020 07:54:28 -0000
From: "tip-bot2 for Peter Zijlstra" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: Sven Schnelle <svens@...ux.ibm.com>,
"Steven Rostedt (VMware)" <rostedt@...dmis.org>,
Thomas Gleixner <tglx@...utronix.de>,
"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
Marco Elver <elver@...gle.com>,
"Peter Zijlstra (Intel)" <peterz@...radead.org>,
x86 <x86@...nel.org>, LKML <linux-kernel@...r.kernel.org>
Subject: [tip: locking/core] lockdep: Use raw_cpu_*() for per-cpu variables
The following commit has been merged into the locking/core branch of tip:
Commit-ID: fddf9055a60dfcc97bda5ef03c8fa4108ed555c5
Gitweb: https://git.kernel.org/tip/fddf9055a60dfcc97bda5ef03c8fa4108ed555c5
Author: Peter Zijlstra <peterz@...radead.org>
AuthorDate: Thu, 20 Aug 2020 09:13:30 +02:00
Committer: Peter Zijlstra <peterz@...radead.org>
CommitterDate: Wed, 26 Aug 2020 12:41:53 +02:00
lockdep: Use raw_cpu_*() for per-cpu variables
Sven reported that commit a21ee6055c30 ("lockdep: Change
hardirq{s_enabled,_context} to per-cpu variables") caused trouble on
s390 because their this_cpu_*() primitives disable preemption which
then lands back tracing.
On the one hand, per-cpu ops should use preempt_*able_notrace() and
raw_local_irq_*(), on the other hand, we can trivialy use raw_cpu_*()
ops for this.
Fixes: a21ee6055c30 ("lockdep: Change hardirq{s_enabled,_context} to per-cpu variables")
Reported-by: Sven Schnelle <svens@...ux.ibm.com>
Reviewed-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
Reviewed-by: Thomas Gleixner <tglx@...utronix.de>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
Tested-by: Marco Elver <elver@...gle.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Link: https://lkml.kernel.org/r/20200821085348.192346882@infradead.org
---
include/linux/irqflags.h | 6 +++---
include/linux/lockdep.h | 18 +++++++++++++-----
kernel/locking/lockdep.c | 4 ++--
3 files changed, 18 insertions(+), 10 deletions(-)
diff --git a/include/linux/irqflags.h b/include/linux/irqflags.h
index bd5c557..d7e50a2 100644
--- a/include/linux/irqflags.h
+++ b/include/linux/irqflags.h
@@ -53,13 +53,13 @@ DECLARE_PER_CPU(int, hardirq_context);
extern void trace_hardirqs_off_finish(void);
extern void trace_hardirqs_on(void);
extern void trace_hardirqs_off(void);
-# define lockdep_hardirq_context() (this_cpu_read(hardirq_context))
+# define lockdep_hardirq_context() (raw_cpu_read(hardirq_context))
# define lockdep_softirq_context(p) ((p)->softirq_context)
# define lockdep_hardirqs_enabled() (this_cpu_read(hardirqs_enabled))
# define lockdep_softirqs_enabled(p) ((p)->softirqs_enabled)
# define lockdep_hardirq_enter() \
do { \
- if (this_cpu_inc_return(hardirq_context) == 1) \
+ if (__this_cpu_inc_return(hardirq_context) == 1)\
current->hardirq_threaded = 0; \
} while (0)
# define lockdep_hardirq_threaded() \
@@ -68,7 +68,7 @@ do { \
} while (0)
# define lockdep_hardirq_exit() \
do { \
- this_cpu_dec(hardirq_context); \
+ __this_cpu_dec(hardirq_context); \
} while (0)
# define lockdep_softirq_enter() \
do { \
diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
index 62a382d..6a584b3 100644
--- a/include/linux/lockdep.h
+++ b/include/linux/lockdep.h
@@ -535,19 +535,27 @@ do { \
DECLARE_PER_CPU(int, hardirqs_enabled);
DECLARE_PER_CPU(int, hardirq_context);
+/*
+ * The below lockdep_assert_*() macros use raw_cpu_read() to access the above
+ * per-cpu variables. This is required because this_cpu_read() will potentially
+ * call into preempt/irq-disable and that obviously isn't right. This is also
+ * correct because when IRQs are enabled, it doesn't matter if we accidentally
+ * read the value from our previous CPU.
+ */
+
#define lockdep_assert_irqs_enabled() \
do { \
- WARN_ON_ONCE(debug_locks && !this_cpu_read(hardirqs_enabled)); \
+ WARN_ON_ONCE(debug_locks && !raw_cpu_read(hardirqs_enabled)); \
} while (0)
#define lockdep_assert_irqs_disabled() \
do { \
- WARN_ON_ONCE(debug_locks && this_cpu_read(hardirqs_enabled)); \
+ WARN_ON_ONCE(debug_locks && raw_cpu_read(hardirqs_enabled)); \
} while (0)
#define lockdep_assert_in_irq() \
do { \
- WARN_ON_ONCE(debug_locks && !this_cpu_read(hardirq_context)); \
+ WARN_ON_ONCE(debug_locks && !raw_cpu_read(hardirq_context)); \
} while (0)
#define lockdep_assert_preemption_enabled() \
@@ -555,7 +563,7 @@ do { \
WARN_ON_ONCE(IS_ENABLED(CONFIG_PREEMPT_COUNT) && \
debug_locks && \
(preempt_count() != 0 || \
- !this_cpu_read(hardirqs_enabled))); \
+ !raw_cpu_read(hardirqs_enabled))); \
} while (0)
#define lockdep_assert_preemption_disabled() \
@@ -563,7 +571,7 @@ do { \
WARN_ON_ONCE(IS_ENABLED(CONFIG_PREEMPT_COUNT) && \
debug_locks && \
(preempt_count() == 0 && \
- this_cpu_read(hardirqs_enabled))); \
+ raw_cpu_read(hardirqs_enabled))); \
} while (0)
#else
diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 2fad21d..c872e95 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -3756,7 +3756,7 @@ void noinstr lockdep_hardirqs_on(unsigned long ip)
skip_checks:
/* we'll do an OFF -> ON transition: */
- this_cpu_write(hardirqs_enabled, 1);
+ __this_cpu_write(hardirqs_enabled, 1);
trace->hardirq_enable_ip = ip;
trace->hardirq_enable_event = ++trace->irq_events;
debug_atomic_inc(hardirqs_on_events);
@@ -3795,7 +3795,7 @@ void noinstr lockdep_hardirqs_off(unsigned long ip)
/*
* We have done an ON -> OFF transition:
*/
- this_cpu_write(hardirqs_enabled, 0);
+ __this_cpu_write(hardirqs_enabled, 0);
trace->hardirq_disable_ip = ip;
trace->hardirq_disable_event = ++trace->irq_events;
debug_atomic_inc(hardirqs_off_events);
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