| Message ID | 20140822140759.GA31775@ada (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Fri, Aug 22, 2014 at 10:07 AM, Andreea-Cristina Bernat <bernat.ada@gmail.com> wrote: > The use of "rcu_assign_pointer()" is NULLing out the pointer. > According to RCU_INIT_POINTER()'s block comment: > "1. This use of RCU_INIT_POINTER() is NULLing out the pointer" > it is better to use it instead of rcu_assign_pointer() because it has a > smaller overhead. > > The following Coccinelle semantic patch was used: > @@ > @@ > > - rcu_assign_pointer > + RCU_INIT_POINTER > (..., NULL) > > Signed-off-by: Andreea-Cristina Bernat <bernat.ada@gmail.com> > --- > fs/nfs/delegation.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/fs/nfs/delegation.c b/fs/nfs/delegation.c > index 5d8ccec..349e63b 100644 > --- a/fs/nfs/delegation.c > +++ b/fs/nfs/delegation.c > @@ -249,7 +249,7 @@ nfs_detach_delegation_locked(struct nfs_inode *nfsi, > list_del_rcu(&delegation->super_list); > delegation->inode = NULL; > nfsi->delegation_state = 0; > - rcu_assign_pointer(nfsi->delegation, NULL); > + RCU_INIT_POINTER(nfsi->delegation, NULL); > spin_unlock(&delegation->lock); > return delegation; > } > -- > 1.9.1 Sorry, but NACK. We do need the memory barriers here, as the nfs_inode is globally visible, and other threads may be checking nfsi->delegation_state and/or delegation->inode in order to conclude whether or not there is still a delegation associated with this inode. Cheers Trond
diff --git a/fs/nfs/delegation.c b/fs/nfs/delegation.c index 5d8ccec..349e63b 100644 --- a/fs/nfs/delegation.c +++ b/fs/nfs/delegation.c @@ -249,7 +249,7 @@ nfs_detach_delegation_locked(struct nfs_inode *nfsi, list_del_rcu(&delegation->super_list); delegation->inode = NULL; nfsi->delegation_state = 0; - rcu_assign_pointer(nfsi->delegation, NULL); + RCU_INIT_POINTER(nfsi->delegation, NULL); spin_unlock(&delegation->lock); return delegation; }
The use of "rcu_assign_pointer()" is NULLing out the pointer. According to RCU_INIT_POINTER()'s block comment: "1. This use of RCU_INIT_POINTER() is NULLing out the pointer" it is better to use it instead of rcu_assign_pointer() because it has a smaller overhead. The following Coccinelle semantic patch was used: @@ @@ - rcu_assign_pointer + RCU_INIT_POINTER (..., NULL) Signed-off-by: Andreea-Cristina Bernat <bernat.ada@gmail.com> --- fs/nfs/delegation.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)