Messages in this thread Patch in this message | | | From | "Paul E. McKenney" <> | Subject | [PATCH tip/core/rcu 09/13] locking/percpu-rwsem: Make percpu_free_rwsem() after kzalloc() safe | Date | Tue, 6 Oct 2015 09:45:30 -0700 |
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From: Oleg Nesterov <oleg@redhat.com>
This is the temporary ugly hack which will be reverted later. We only need it to ensure that the next patch will not break "change sb_writers to use percpu_rw_semaphore" patches routed via the VFS tree.
The alloc_super()->destroy_super() error path assumes that it is safe to call percpu_free_rwsem() after kzalloc() without percpu_init_rwsem(), so let's not disappoint it.
Signed-off-by: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> --- kernel/locking/percpu-rwsem.c | 7 +++++++ 1 file changed, 7 insertions(+)
diff --git a/kernel/locking/percpu-rwsem.c b/kernel/locking/percpu-rwsem.c index e2621fbbcbd1..9529a30ec57b 100644 --- a/kernel/locking/percpu-rwsem.c +++ b/kernel/locking/percpu-rwsem.c @@ -26,6 +26,13 @@ EXPORT_SYMBOL_GPL(__percpu_init_rwsem); void percpu_free_rwsem(struct percpu_rw_semaphore *brw) { + /* + * XXX: temporary kludge. The error path in alloc_super() + * assumes that percpu_free_rwsem() is safe after kzalloc(). + */ + if (!brw->fast_read_ctr) + return; + free_percpu(brw->fast_read_ctr); brw->fast_read_ctr = NULL; /* catch use after free bugs */ } -- 2.5.2
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