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authorOlaf Faaland <[email protected]>2015-10-15 13:08:27 -0700
committerBrian Behlendorf <[email protected]>2015-12-22 10:21:33 -0800
commit448d7aaabc55b43663c597b91b221bed982d81dd (patch)
tree89e12793ce08d38389662ff18c9336ba4be7fb9c /module/zfs/multilist.c
parente0553a74adf1b1035e1ae25ca7feacacdeb93931 (diff)
Identify locks flagged by lockdep
When running a kernel with CONFIG_LOCKDEP=y, lockdep reports possible recursive locking in some cases and possible circular locking dependency in others, within the SPL and ZFS modules. This patch uses a mutex type defined in SPL, MUTEX_NOLOCKDEP, to mark such mutexes when they are initialized. This mutex type causes attempts to take or release those locks to be wrapped in lockdep_off() and lockdep_on() calls to silence the dependency checker and allow the use of lock_stats to examine contention. For RW locks, it uses an analogous lock type, RW_NOLOCKDEP. The goal is that these locks are ultimately changed back to type MUTEX_DEFAULT or RW_DEFAULT, after the locks are annotated to reflect their relationship (e.g. z_name_lock below) or any real problem with the lock dependencies are fixed. Some of the affected locks are: tc_open_lock: ============= This is an array of locks, all with same name, which txg_quiesce must take all of in order to move txg to next state. All default to the same lockdep class, and so to lockdep appears recursive. zp->z_name_lock: ================ In zfs_rmdir, dzp = znode for the directory (input to zfs_dirent_lock) zp = znode for the entry being removed (output of zfs_dirent_lock) zfs_rmdir()->zfs_dirent_lock() takes z_name_lock in dzp zfs_rmdir() takes z_name_lock in zp Since both dzp and zp are type znode_t, the locks have the same default class, and lockdep considers it a possible recursive lock attempt. l->l_rwlock: ============ zap_expand_leaf() sometimes creates two new zap leaf structures, via these call paths: zap_deref_leaf()->zap_get_leaf_byblk()->zap_leaf_open() zap_expand_leaf()->zap_create_leaf()->zap_expand_leaf()->zap_create_leaf() Because both zap_leaf_open() and zap_create_leaf() initialize l->l_rwlock in their (separate) leaf structures, the lockdep class is the same, and the linux kernel believes these might both be the same lock, and emits a possible recursive lock warning. Signed-off-by: Olaf Faaland <[email protected]> Signed-off-by: Brian Behlendorf <[email protected]> Closes #3895
Diffstat (limited to 'module/zfs/multilist.c')
-rw-r--r--module/zfs/multilist.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/module/zfs/multilist.c b/module/zfs/multilist.c
index e4446ded2..e02a4bae3 100644
--- a/module/zfs/multilist.c
+++ b/module/zfs/multilist.c
@@ -85,7 +85,7 @@ multilist_create(multilist_t *ml, size_t size, size_t offset, unsigned int num,
for (i = 0; i < ml->ml_num_sublists; i++) {
multilist_sublist_t *mls = &ml->ml_sublists[i];
- mutex_init(&mls->mls_lock, NULL, MUTEX_DEFAULT, NULL);
+ mutex_init(&mls->mls_lock, NULL, MUTEX_NOLOCKDEP, NULL);
list_create(&mls->mls_list, size, offset);
}
}