[PATCH tip/core/urgent 10/10] vfs: fix RCU-lockdep false positive due to /proc access
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From: Paul E. McKenney on 30 Apr 2010 20:30 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. Located-by: Miles Lane <miles.lane(a)gmail.com> Located-by: Eric Dumazet <eric.dumazet(a)gmail.com> Signed-off-by: Paul E. McKenney <paulmck(a)linux.vnet.ibm.com> --- 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 013dc52..e4a6d31 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 || \ + thread_group_empty(current))) #define files_fdtable(files) \ (rcu_dereference_check_fdtable((files), (files)->fdt)) -- 1.7.0 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |