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>
Impact: cleanup
We want to remove percpu.h from rcupdate.h (for upcoming kmemtrace
changes), but this is not possible currently without breaking the
build because fdtable.h has an implicit include file dependency: it
uses __init does not include init.h.
This can cause build failures on non-x86 architectures:
/home/mingo/tip/include/linux/fdtable.h:66: error: expected '=', ',',
';', 'asm' or '__attribute__' before 'files_defer_init'
make[2]: *** [fs/locks.o] Error 1
We got this header included indirectly via rcupdate.h's percpu.h
inclusion - but if that is not there the build will break.
Fix it.
Cc: Pekka Enberg <penberg@cs.helsinki.fi>
Cc: Eduard - Gabriel Munteanu <eduard.munteanu@linux360.ro>
Cc: paulmck@linux.vnet.ibm.com
LKML-Reference: <1237898630.25315.83.camel@penberg-laptop>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Instead of creating the "filp" kmem_cache in vfs_caches_init(),
we can do it a litle be later in files_init(), so that filp_cachep
is static to fs/file_table.c
Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
