104 lines
3.0 KiB
Diff
104 lines
3.0 KiB
Diff
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From c3e639bc522bac3c706ec59f0fe927af2c5f4a5a Mon Sep 17 00:00:00 2001
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From: Josh Cartwright <joshc@ni.com>
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Date: Thu, 31 Mar 2016 00:04:25 -0500
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Subject: [PATCH 095/365] list_bl: fixup bogus lockdep warning
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At first glance, the use of 'static inline' seems appropriate for
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INIT_HLIST_BL_HEAD().
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However, when a 'static inline' function invocation is inlined by gcc,
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all callers share any static local data declared within that inline
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function.
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This presents a problem for how lockdep classes are setup. raw_spinlocks, for
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example, when CONFIG_DEBUG_SPINLOCK,
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# define raw_spin_lock_init(lock) \
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do { \
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static struct lock_class_key __key; \
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\
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__raw_spin_lock_init((lock), #lock, &__key); \
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} while (0)
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When this macro is expanded into a 'static inline' caller, like
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INIT_HLIST_BL_HEAD():
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static inline INIT_HLIST_BL_HEAD(struct hlist_bl_head *h)
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{
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h->first = NULL;
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raw_spin_lock_init(&h->lock);
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}
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...the static local lock_class_key object is made a function static.
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For compilation units which initialize invoke INIT_HLIST_BL_HEAD() more
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than once, then, all of the invocations share this same static local
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object.
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This can lead to some very confusing lockdep splats (example below).
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Solve this problem by forcing the INIT_HLIST_BL_HEAD() to be a macro,
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which prevents the lockdep class object sharing.
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=============================================
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[ INFO: possible recursive locking detected ]
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4.4.4-rt11 #4 Not tainted
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---------------------------------------------
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kswapd0/59 is trying to acquire lock:
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(&h->lock#2){+.+.-.}, at: mb_cache_shrink_scan
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but task is already holding lock:
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(&h->lock#2){+.+.-.}, at: mb_cache_shrink_scan
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other info that might help us debug this:
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Possible unsafe locking scenario:
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CPU0
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----
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lock(&h->lock#2);
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lock(&h->lock#2);
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*** DEADLOCK ***
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May be due to missing lock nesting notation
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2 locks held by kswapd0/59:
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#0: (shrinker_rwsem){+.+...}, at: rt_down_read_trylock
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#1: (&h->lock#2){+.+.-.}, at: mb_cache_shrink_scan
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Reported-by: Luis Claudio R. Goncalves <lclaudio@uudg.org>
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Tested-by: Luis Claudio R. Goncalves <lclaudio@uudg.org>
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Signed-off-by: Josh Cartwright <joshc@ni.com>
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Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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---
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include/linux/list_bl.h | 12 +++++++-----
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1 file changed, 7 insertions(+), 5 deletions(-)
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diff --git a/include/linux/list_bl.h b/include/linux/list_bl.h
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index d3af0990f01a..4e5062316bb6 100644
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--- a/include/linux/list_bl.h
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+++ b/include/linux/list_bl.h
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@@ -42,13 +42,15 @@ struct hlist_bl_node {
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struct hlist_bl_node *next, **pprev;
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};
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-static inline void INIT_HLIST_BL_HEAD(struct hlist_bl_head *h)
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-{
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- h->first = NULL;
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#ifdef CONFIG_PREEMPT_RT_BASE
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- raw_spin_lock_init(&h->lock);
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+#define INIT_HLIST_BL_HEAD(h) \
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+do { \
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+ (h)->first = NULL; \
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+ raw_spin_lock_init(&(h)->lock); \
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+} while (0)
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+#else
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+#define INIT_HLIST_BL_HEAD(h) (h)->first = NULL
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#endif
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-}
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static inline void INIT_HLIST_BL_NODE(struct hlist_bl_node *h)
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{
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--
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2.28.0
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