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authorMark Rutland <mark.rutland@arm.com>2021-01-11 15:37:07 +0000
committerPeter Zijlstra <peterz@infradead.org>2021-01-22 11:08:56 +0100
commit997acaf6b4b59c6a9c259740312a69ea549cc684 (patch)
tree5cd5df4d2df07bf6646a08658de2df458def237b /lib/Kconfig.debug
parent2f0df49c89acaa58571d509830bc481250699885 (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 'lib/Kconfig.debug')
-rw-r--r--lib/Kconfig.debug8
1 files changed, 8 insertions, 0 deletions
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index e6e58b26e888..78eadf615df8 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