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| 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 /lib/Kconfig.debug | |
| parent | 2f0df49c89acaa58571d509830bc481250699885 (diff) | |
| download | lwn-997acaf6b4b59c6a9c259740312a69ea549cc684.tar.gz lwn-997acaf6b4b59c6a9c259740312a69ea549cc684.zip | |
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.debug | 8 |
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 |