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![Steven Whitehouse](/assets/img/avatar_default.png)
Abhi noticed that we were getting a complaint from the RCU subsystem about access of an RCU protected list under the write side bit lock. This commit adds additional annotation to check both the RCU read lock and the write side bit lock before printing a message. Reported by: Abhijith Das <adas@redhat.com> Signed-off-by: Steven Whitehouse <swhiteho@redhat.com> Tested-by: Abhijith Das <adas@redhat.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
128 lines
4.3 KiB
C
128 lines
4.3 KiB
C
#ifndef _LINUX_RCULIST_BL_H
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#define _LINUX_RCULIST_BL_H
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/*
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* RCU-protected bl list version. See include/linux/list_bl.h.
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*/
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#include <linux/list_bl.h>
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#include <linux/rcupdate.h>
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static inline void hlist_bl_set_first_rcu(struct hlist_bl_head *h,
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struct hlist_bl_node *n)
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{
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LIST_BL_BUG_ON((unsigned long)n & LIST_BL_LOCKMASK);
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LIST_BL_BUG_ON(((unsigned long)h->first & LIST_BL_LOCKMASK) !=
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LIST_BL_LOCKMASK);
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rcu_assign_pointer(h->first,
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(struct hlist_bl_node *)((unsigned long)n | LIST_BL_LOCKMASK));
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}
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static inline struct hlist_bl_node *hlist_bl_first_rcu(struct hlist_bl_head *h)
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{
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return (struct hlist_bl_node *)
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((unsigned long)rcu_dereference_check(h->first, hlist_bl_is_locked(h)) & ~LIST_BL_LOCKMASK);
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}
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/**
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* hlist_bl_del_init_rcu - deletes entry from hash list with re-initialization
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* @n: the element to delete from the hash list.
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*
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* Note: hlist_bl_unhashed() on the node returns true after this. It is
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* useful for RCU based read lockfree traversal if the writer side
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* must know if the list entry is still hashed or already unhashed.
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*
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* In particular, it means that we can not poison the forward pointers
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* that may still be used for walking the hash list and we can only
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* zero the pprev pointer so list_unhashed() will return true after
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* this.
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*
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* The caller must take whatever precautions are necessary (such as
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* holding appropriate locks) to avoid racing with another
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* list-mutation primitive, such as hlist_bl_add_head_rcu() or
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* hlist_bl_del_rcu(), running on this same list. However, it is
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* perfectly legal to run concurrently with the _rcu list-traversal
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* primitives, such as hlist_bl_for_each_entry_rcu().
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*/
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static inline void hlist_bl_del_init_rcu(struct hlist_bl_node *n)
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{
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if (!hlist_bl_unhashed(n)) {
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__hlist_bl_del(n);
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n->pprev = NULL;
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}
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}
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/**
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* hlist_bl_del_rcu - deletes entry from hash list without re-initialization
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* @n: the element to delete from the hash list.
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*
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* Note: hlist_bl_unhashed() on entry does not return true after this,
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* the entry is in an undefined state. It is useful for RCU based
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* lockfree traversal.
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*
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* In particular, it means that we can not poison the forward
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* pointers that may still be used for walking the hash list.
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*
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* The caller must take whatever precautions are necessary
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* (such as holding appropriate locks) to avoid racing
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* with another list-mutation primitive, such as hlist_bl_add_head_rcu()
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* or hlist_bl_del_rcu(), running on this same list.
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* However, it is perfectly legal to run concurrently with
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* the _rcu list-traversal primitives, such as
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* hlist_bl_for_each_entry().
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*/
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static inline void hlist_bl_del_rcu(struct hlist_bl_node *n)
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{
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__hlist_bl_del(n);
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n->pprev = LIST_POISON2;
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}
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/**
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* hlist_bl_add_head_rcu
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* @n: the element to add to the hash list.
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* @h: the list to add to.
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*
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* Description:
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* Adds the specified element to the specified hlist_bl,
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* while permitting racing traversals.
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*
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* The caller must take whatever precautions are necessary
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* (such as holding appropriate locks) to avoid racing
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* with another list-mutation primitive, such as hlist_bl_add_head_rcu()
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* or hlist_bl_del_rcu(), running on this same list.
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* However, it is perfectly legal to run concurrently with
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* the _rcu list-traversal primitives, such as
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* hlist_bl_for_each_entry_rcu(), used to prevent memory-consistency
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* problems on Alpha CPUs. Regardless of the type of CPU, the
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* list-traversal primitive must be guarded by rcu_read_lock().
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*/
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static inline void hlist_bl_add_head_rcu(struct hlist_bl_node *n,
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struct hlist_bl_head *h)
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{
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struct hlist_bl_node *first;
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/* don't need hlist_bl_first_rcu because we're under lock */
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first = hlist_bl_first(h);
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n->next = first;
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if (first)
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first->pprev = &n->next;
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n->pprev = &h->first;
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/* need _rcu because we can have concurrent lock free readers */
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hlist_bl_set_first_rcu(h, n);
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}
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/**
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* hlist_bl_for_each_entry_rcu - iterate over rcu list of given type
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* @tpos: the type * to use as a loop cursor.
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* @pos: the &struct hlist_bl_node to use as a loop cursor.
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* @head: the head for your list.
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* @member: the name of the hlist_bl_node within the struct.
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*
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*/
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#define hlist_bl_for_each_entry_rcu(tpos, pos, head, member) \
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for (pos = hlist_bl_first_rcu(head); \
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pos && \
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({ tpos = hlist_bl_entry(pos, typeof(*tpos), member); 1; }); \
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pos = rcu_dereference_raw(pos->next))
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#endif
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