tree: git://git.linux-nfs.org/projects/trondmy/linux-nfs.git testing
head: c925dd1e826cb81f1dafef462b1326ec33913b8e
commit: 9d097c9f0dd73d0e02ddfceb112e3bcdd8915524 [41/45] NFS: Convert lookups of the lock context to RCU
reproduce:
# apt-get install sparse
git checkout 9d097c9f0dd73d0e02ddfceb112e3bcdd8915524
make ARCH=x86_64 allmodconfig
make C=1 CF=-D__CHECK_ENDIAN__
sparse warnings: (new ones prefixed by >>)
include/linux/nfs_fs.h:566:16: sparse: expression using sizeof(void)
include/linux/nfs_fs.h:566:16: sparse: expression using sizeof(void)
include/linux/nfs_fs.h:566:16: sparse: expression using sizeof(void)
include/linux/nfs_fs.h:566:16: sparse: expression using sizeof(void)
include/linux/nfs_fs.h:566:16: sparse: expression using sizeof(void)
>> include/linux/rculist.h:130:25: sparse: context imbalance in 'nfs_put_lock_context' - unexpected unlock
include/linux/list.h:125:25: sparse: context imbalance in '__put_nfs_open_context' - unexpected unlock
vim +/nfs_put_lock_context +130 include/linux/rculist.h
82524746 Franck Bui-Huu 2008-05-12 103
82524746 Franck Bui-Huu 2008-05-12 104 /**
82524746 Franck Bui-Huu 2008-05-12 105 * list_del_rcu - deletes entry from list without re-initialization
82524746 Franck Bui-Huu 2008-05-12 106 * @entry: the element to delete from the list.
82524746 Franck Bui-Huu 2008-05-12 107 *
82524746 Franck Bui-Huu 2008-05-12 108 * Note: list_empty() on entry does not return true after this,
82524746 Franck Bui-Huu 2008-05-12 109 * the entry is in an undefined state. It is useful for RCU based
82524746 Franck Bui-Huu 2008-05-12 110 * lockfree traversal.
82524746 Franck Bui-Huu 2008-05-12 111 *
82524746 Franck Bui-Huu 2008-05-12 112 * In particular, it means that we can not poison the forward
82524746 Franck Bui-Huu 2008-05-12 113 * pointers that may still be used for walking the list.
82524746 Franck Bui-Huu 2008-05-12 114 *
82524746 Franck Bui-Huu 2008-05-12 115 * The caller must take whatever precautions are necessary
82524746 Franck Bui-Huu 2008-05-12 116 * (such as holding appropriate locks) to avoid racing
82524746 Franck Bui-Huu 2008-05-12 117 * with another list-mutation primitive, such as list_del_rcu()
82524746 Franck Bui-Huu 2008-05-12 118 * or list_add_rcu(), running on this same list.
82524746 Franck Bui-Huu 2008-05-12 119 * However, it is perfectly legal to run concurrently with
82524746 Franck Bui-Huu 2008-05-12 120 * the _rcu list-traversal primitives, such as
82524746 Franck Bui-Huu 2008-05-12 121 * list_for_each_entry_rcu().
82524746 Franck Bui-Huu 2008-05-12 122 *
82524746 Franck Bui-Huu 2008-05-12 123 * Note that the caller is not permitted to immediately free
82524746 Franck Bui-Huu 2008-05-12 124 * the newly deleted entry. Instead, either synchronize_rcu()
82524746 Franck Bui-Huu 2008-05-12 125 * or call_rcu() must be used to defer freeing until an RCU
82524746 Franck Bui-Huu 2008-05-12 126 * grace period has elapsed.
82524746 Franck Bui-Huu 2008-05-12 127 */
82524746 Franck Bui-Huu 2008-05-12 128 static inline void list_del_rcu(struct list_head *entry)
82524746 Franck Bui-Huu 2008-05-12 129 {
559f9bad Dave Jones 2012-03-14 @130 __list_del_entry(entry);
82524746 Franck Bui-Huu 2008-05-12 131 entry->prev = LIST_POISON2;
82524746 Franck Bui-Huu 2008-05-12 132 }
82524746 Franck Bui-Huu 2008-05-12 133
:::::: The code at line 130 was first introduced by commit
:::::: 559f9badd11ddf399f88b18b4c0f110fd511ae53 rcu: List-debug variants of rcu list routines.
:::::: TO: Dave Jones <davej@xxxxxxxxxx>
:::::: CC: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
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