[PATCH] genirq: Ensure flags in lock guard is consistently initialized

[PATCH] genirq: Ensure flags in lock guard is consistently initialized

[Nathan Chancellor]

After the conversion to locking guards within the interrupt core code,
several builds with clang show the "Interrupts were enabled early"
WARN() in start_kernel() on boot.

In class_irqdesc_lock_constructor(), _t.flags is initialized via
__irq_get_desc_lock() within the _t initializer list. However, the C11
standard 6.7.9.23 states that the evaluation of the initialization list
expressions are indeterminately sequenced relative to one another,
meaning _t.flags could be initialized by __irq_get_desc_lock() then be
initialized to zero due to flags being absent from the initializer list.

To ensure _t.flags is consistently initialized, move the call to
__irq_get_desc_lock() and the assignment of its result to _t.lock out of
the designated initializer.

Fixes: 0f70a49f3fa3 ("genirq: Provide conditional lock guards")
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
---
 kernel/irq/internals.h | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/kernel/irq/internals.h b/kernel/irq/internals.h
index bd2db6ebb98e..476a20fd9bfc 100644
--- a/kernel/irq/internals.h
+++ b/kernel/irq/internals.h
@@ -176,10 +176,10 @@ __DEFINE_UNLOCK_GUARD(irqdesc_lock, struct irq_desc,
 static inline class_irqdesc_lock_t class_irqdesc_lock_constructor(unsigned int irq, bool bus,
 								  unsigned int check)
 {
-	class_irqdesc_lock_t _t = {
-		.bus	= bus,
-		.lock	= __irq_get_desc_lock(irq, &_t.flags, bus, check),
-	};
+	class_irqdesc_lock_t _t = { .bus = bus, };
+
+	_t.lock = __irq_get_desc_lock(irq, &_t.flags, bus, check);
+
 	return _t;
 }
 

---
base-commit: c1ab449df871d6ce9189cb0a9efcd37d2ead10f0
change-id: 20250512-irq-guards-fix-flags-init-1243eabe3401

Best regards,
-- 
Nathan Chancellor <nathan@kernel.org>

Re: [PATCH] genirq: Ensure flags in lock guard is consistently initialized

[Jiri Slaby]

On 13. 05. 25, 0:16, Nathan Chancellor wrote:
> After the conversion to locking guards within the interrupt core code,
> several builds with clang show the "Interrupts were enabled early"
> WARN() in start_kernel() on boot.
> 
> In class_irqdesc_lock_constructor(), _t.flags is initialized via
> __irq_get_desc_lock() within the _t initializer list. However, the C11
> standard 6.7.9.23 states that the evaluation of the initialization list
> expressions are indeterminately sequenced relative to one another,
> meaning _t.flags could be initialized by __irq_get_desc_lock() then be
> initialized to zero due to flags being absent from the initializer list.
> 
> To ensure _t.flags is consistently initialized, move the call to
> __irq_get_desc_lock() and the assignment of its result to _t.lock out of
> the designated initializer.
> 
> Fixes: 0f70a49f3fa3 ("genirq: Provide conditional lock guards")
> Signed-off-by: Nathan Chancellor <nathan@kernel.org>

Reviewed-by: Jiri Slaby <jirislaby@kernel.org>

thanks,
-- 
js
suse labs