notifier: Initialize new struct srcu_usage field

In commit 95433f726301 ("srcu: Begin offloading srcu_struct fields to srcu_update"), a new struct srcu_usage field was added, but was not properly initialized. This led to a "spinlock bad magic" BUG when the SRCU notifier was ever used. This was observed in the MediaTek CCI devfreq driver on next-20230525. The trimmed stack trace is as follows: BUG: spinlock bad magic on CPU#4, swapper/0/1 lock: 0xffffff80ff529ac0, .magic: 00000000, .owner: <none>/-1, .owner_cpu: 0 Call trace: spin_bug+0xa4/0xe8 do_raw_spin_lock+0xec/0x120 _raw_spin_lock_irqsave+0x78/0xb8 synchronize_srcu+0x3c/0x168 srcu_notifier_chain_unregister+0x5c/0xa0 cpufreq_unregister_notifier+0x94/0xe0 devfreq_passive_event_handler+0x7c/0x3e0 devfreq_remove_device+0x48/0xe8 Add __SRCU_USAGE_INIT() to SRCU_NOTIFIER_INIT() so that srcu_usage gets initialized properly.

Chen-Yu Tsai committed 3 years ago

Commit de29a961 parent ac9a7861 file · +10 −0Browse files

Unified · Split

include/linux/notifier.h+10−0

@@ -106,12 +106,22 @@ extern void srcu_init_notifier_head(struct srcu_notifier_head *nh); · 105 unmodified lines
106	106	#define RAW_NOTIFIER_INIT(name) { \
107	107	.head = NULL }
108	108
	109	+#ifdef CONFIG_TREE_SRCU
109	110	#define SRCU_NOTIFIER_INIT(name, pcpu) \
110	111	{ \
111	112	.mutex = __MUTEX_INITIALIZER(name.mutex), \
112	113	.head = NULL, \
	114	+ .srcuu = __SRCU_USAGE_INIT(name.srcuu), \
113	115	.srcu = __SRCU_STRUCT_INIT(name.srcu, name.srcuu, pcpu), \
114	116	}
	117	+#else
	118	+#define SRCU_NOTIFIER_INIT(name, pcpu) \
	119	+ { \
	120	+ .mutex = __MUTEX_INITIALIZER(name.mutex), \
	121	+ .head = NULL, \
	122	+ .srcu = __SRCU_STRUCT_INIT(name.srcu, name.srcuu, pcpu), \
	123	+ }
	124	+#endif
115	125
116	126	#define ATOMIC_NOTIFIER_HEAD(name) \
117	127	struct atomic_notifier_head name = \