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| author | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2010-07-20 13:24:34 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2010-07-20 16:25:41 -0700 |
| commit | 844b9a8707f1fcf0482e0c52f44a555e799ccda6 (patch) | |
| tree | c9c095c123c2988b014e39b461eb04411b3a197d /include/linux/fdtable.h | |
| parent | 9d51a6b2487724e8713cd2794cf09ffeee5f6932 (diff) | |
| download | lwn-844b9a8707f1fcf0482e0c52f44a555e799ccda6.tar.gz lwn-844b9a8707f1fcf0482e0c52f44a555e799ccda6.zip | |
vfs: fix RCU-lockdep false positive due to /proc
If a single-threaded process does a file-descriptor operation, and some
other process accesses that same file descriptor via /proc, the current
rcu_dereference_check_fdtable() can give a false-positive RCU-lockdep
splat due to the reference count being increased by the /proc access after
the reference-count check in fget_light() but before the check in
rcu_dereference_check_fdtable().
This commit prevents this false positive by checking for a single-threaded
process. To avoid #include hell, this commit uses the wrapper for
thread_group_empty(current) defined by rcu_my_thread_group_empty()
provided in a separate commit.
Located-by: Miles Lane <miles.lane@gmail.com>
Located-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include/linux/fdtable.h')
| -rw-r--r-- | include/linux/fdtable.h | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/include/linux/fdtable.h b/include/linux/fdtable.h index 013dc529e95f..d147461bc271 100644 --- a/include/linux/fdtable.h +++ b/include/linux/fdtable.h @@ -61,7 +61,8 @@ struct files_struct { (rcu_dereference_check((fdtfd), \ rcu_read_lock_held() || \ lockdep_is_held(&(files)->file_lock) || \ - atomic_read(&(files)->count) == 1)) + atomic_read(&(files)->count) == 1 || \ + rcu_my_thread_group_empty())) #define files_fdtable(files) \ (rcu_dereference_check_fdtable((files), (files)->fdt)) |