diff options
| author | Mark Rutland <mark.rutland@arm.com> | 2021-01-11 15:37:07 +0000 |
|---|---|---|
| committer | Peter Zijlstra <peterz@infradead.org> | 2021-01-22 11:08:56 +0100 |
| commit | 997acaf6b4b59c6a9c259740312a69ea549cc684 (patch) | |
| tree | 5cd5df4d2df07bf6646a08658de2df458def237b /kernel/locking | |
| parent | 2f0df49c89acaa58571d509830bc481250699885 (diff) | |
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
Diffstat (limited to 'kernel/locking')
| -rw-r--r-- | kernel/locking/Makefile | 1 | ||||
| -rw-r--r-- | kernel/locking/irqflag-debug.c | 11 |
2 files changed, 12 insertions, 0 deletions
diff --git a/kernel/locking/Makefile b/kernel/locking/Makefile index 6d11cfb9b41f..8838f1d7c4a2 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 000000000000..9603d207a4ca --- /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); |