From: "tip-bot2 for Mark Rutland" <tip-bot2@linutronix.de>
To: linux-tip-commits@vger.kernel.org
Cc: Mark Rutland <mark.rutland@arm.com>,
"Peter Zijlstra (Intel)" <peterz@infradead.org>,
x86@kernel.org, linux-kernel@vger.kernel.org
Subject: [tip: locking/core] lockdep: report broken irq restoration
Date: Fri, 22 Jan 2021 14:05:27 -0000 [thread overview]
Message-ID: <161132432734.414.7901255699341809699.tip-bot2@tip-bot2> (raw)
In-Reply-To: <20210111153707.10071-1-mark.rutland@arm.com>
The following commit has been merged into the locking/core branch of tip:
Commit-ID: 997acaf6b4b59c6a9c259740312a69ea549cc684
Gitweb: https://git.kernel.org/tip/997acaf6b4b59c6a9c259740312a69ea549cc684
Author: Mark Rutland <mark.rutland@arm.com>
AuthorDate: Mon, 11 Jan 2021 15:37:07
Committer: Peter Zijlstra <peterz@infradead.org>
CommitterDate: Fri, 22 Jan 2021 11:08:56 +01:00
lockdep: report broken irq restoration
We generally expect local_irq_save() and local_irq_restore() to be
paired and sanely nested, and so local_irq_restore() expects to be
called with irqs disabled. Thus, within local_irq_restore() we only
trace irq flag changes when unmasking irqs.
This means that a sequence such as:
| local_irq_disable();
| local_irq_save(flags);
| local_irq_enable();
| local_irq_restore(flags);
... is liable to break things, as the local_irq_restore() would mask
irqs without tracing this change. Similar problems may exist for
architectures whose arch_irq_restore() function depends on being called
with irqs disabled.
We don't consider such sequences to be a good idea, so let's define
those as forbidden, and add tooling to detect such broken cases.
This patch adds debug code to WARN() when raw_local_irq_restore() is
called with irqs enabled. As raw_local_irq_restore() is expected to pair
with raw_local_irq_save(), it should never be called with irqs enabled.
To avoid the possibility of circular header dependencies between
irqflags.h and bug.h, the warning is handled in a separate C file.
The new code is all conditional on a new CONFIG_DEBUG_IRQFLAGS symbol
which is independent of CONFIG_TRACE_IRQFLAGS. As noted above such cases
will confuse lockdep, so CONFIG_DEBUG_LOCKDEP now selects
CONFIG_DEBUG_IRQFLAGS.
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20210111153707.10071-1-mark.rutland@arm.com
---
include/linux/irqflags.h | 12 ++++++++++++
kernel/locking/Makefile | 1 +
kernel/locking/irqflag-debug.c | 11 +++++++++++
lib/Kconfig.debug | 8 ++++++++
4 files changed, 32 insertions(+)
create mode 100644 kernel/locking/irqflag-debug.c
diff --git a/include/linux/irqflags.h b/include/linux/irqflags.h
index 8de0e13..600c10d 100644
--- a/include/linux/irqflags.h
+++ b/include/linux/irqflags.h
@@ -149,6 +149,17 @@ do { \
# define start_critical_timings() do { } while (0)
#endif
+#ifdef CONFIG_DEBUG_IRQFLAGS
+extern void warn_bogus_irq_restore(void);
+#define raw_check_bogus_irq_restore() \
+ do { \
+ if (unlikely(!arch_irqs_disabled())) \
+ warn_bogus_irq_restore(); \
+ } while (0)
+#else
+#define raw_check_bogus_irq_restore() do { } while (0)
+#endif
+
/*
* Wrap the arch provided IRQ routines to provide appropriate checks.
*/
@@ -162,6 +173,7 @@ do { \
#define raw_local_irq_restore(flags) \
do { \
typecheck(unsigned long, flags); \
+ raw_check_bogus_irq_restore(); \
arch_local_irq_restore(flags); \
} while (0)
#define raw_local_save_flags(flags) \
diff --git a/kernel/locking/Makefile b/kernel/locking/Makefile
index 6d11cfb..8838f1d 100644
--- a/kernel/locking/Makefile
+++ b/kernel/locking/Makefile
@@ -15,6 +15,7 @@ CFLAGS_REMOVE_mutex-debug.o = $(CC_FLAGS_FTRACE)
CFLAGS_REMOVE_rtmutex-debug.o = $(CC_FLAGS_FTRACE)
endif
+obj-$(CONFIG_DEBUG_IRQFLAGS) += irqflag-debug.o
obj-$(CONFIG_DEBUG_MUTEXES) += mutex-debug.o
obj-$(CONFIG_LOCKDEP) += lockdep.o
ifeq ($(CONFIG_PROC_FS),y)
diff --git a/kernel/locking/irqflag-debug.c b/kernel/locking/irqflag-debug.c
new file mode 100644
index 0000000..9603d20
--- /dev/null
+++ b/kernel/locking/irqflag-debug.c
@@ -0,0 +1,11 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+#include <linux/bug.h>
+#include <linux/export.h>
+#include <linux/irqflags.h>
+
+void warn_bogus_irq_restore(void)
+{
+ WARN_ONCE(1, "raw_local_irq_restore() called with IRQs enabled\n");
+}
+EXPORT_SYMBOL(warn_bogus_irq_restore);
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index e6e58b2..78eadf6 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1343,6 +1343,7 @@ config LOCKDEP_SMALL
config DEBUG_LOCKDEP
bool "Lock dependency engine debugging"
depends on DEBUG_KERNEL && LOCKDEP
+ select DEBUG_IRQFLAGS
help
If you say Y here, the lock dependency engine will do
additional runtime checks to debug itself, at the price
@@ -1431,6 +1432,13 @@ config TRACE_IRQFLAGS_NMI
depends on TRACE_IRQFLAGS
depends on TRACE_IRQFLAGS_NMI_SUPPORT
+config DEBUG_IRQFLAGS
+ bool "Debug IRQ flag manipulation"
+ help
+ Enables checks for potentially unsafe enabling or disabling of
+ interrupts, such as calling raw_local_irq_restore() when interrupts
+ are enabled.
+
config STACKTRACE
bool "Stack backtrace support"
depends on STACKTRACE_SUPPORT
prev parent reply other threads:[~2021-01-22 14:14 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-11 15:37 [PATCHv2] lockdep: report broken irq restoration Mark Rutland
2021-01-22 11:06 ` Mark Rutland
2021-01-22 13:24 ` Peter Zijlstra
2021-01-22 13:49 ` Mark Rutland
2021-01-22 14:05 ` tip-bot2 for Mark Rutland [this message]
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