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    SubjectRe: Subject: [PATCH] net/ipv6: Use GFP_ATOMIC when a lock is held
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    Le dimanche 30 mai 2010 à 21:48 +0200, Julia Lawall a écrit :
    > From: Julia Lawall <julia@diku.dk>
    >
    > A spin lock is taken near the beginning of the enclosing function.
    >
    > The semantic patch that makes this change is as follows:
    > (http://coccinelle.lip6.fr/)
    >
    > // <smpl>
    > @@
    > @@
    >
    > spin_lock(...)
    > ... when != spin_unlock(...)
    > -GFP_KERNEL
    > +GFP_ATOMIC
    > // </smpl>
    >
    > Signed-off-by: Julia Lawall <julia@diku.dk>
    >
    > ---
    > net/ipv6/sit.c | 2 +-
    > 1 file changed, 1 insertion(+), 1 deletion(-)
    >
    > diff -u -p a/net/ipv6/sit.c b/net/ipv6/sit.c
    > --- a/net/ipv6/sit.c
    > +++ b/net/ipv6/sit.c
    > @@ -358,7 +358,7 @@ ipip6_tunnel_add_prl(struct ip_tunnel *t
    > goto out;
    > }
    >
    > - p = kzalloc(sizeof(struct ip_tunnel_prl_entry), GFP_KERNEL);
    > + p = kzalloc(sizeof(struct ip_tunnel_prl_entry), GFP_ATOMIC);
    > if (!p) {
    > err = -ENOBUFS;
    > goto out;

    Nice catch, but what about allocating this outside of the locked
    section ?

    diff --git a/net/ipv6/sit.c b/net/ipv6/sit.c
    index e51e650..ff3dd84 100644
    --- a/net/ipv6/sit.c
    +++ b/net/ipv6/sit.c
    @@ -340,6 +340,10 @@ ipip6_tunnel_add_prl(struct ip_tunnel *t, struct ip_tunnel_prl *a, int chg)
    if (a->addr == htonl(INADDR_ANY))
    return -EINVAL;

    + p = kzalloc(sizeof(struct ip_tunnel_prl_entry), GFP_KERNEL);
    + if (!p)
    + return -ENOBUFS;
    +
    spin_lock(&ipip6_prl_lock);

    for (p = t->prl; p; p = p->next) {
    @@ -358,19 +362,16 @@ ipip6_tunnel_add_prl(struct ip_tunnel *t, struct ip_tunnel_prl *a, int chg)
    goto out;
    }

    - p = kzalloc(sizeof(struct ip_tunnel_prl_entry), GFP_KERNEL);
    - if (!p) {
    - err = -ENOBUFS;
    - goto out;
    - }

    p->next = t->prl;
    p->addr = a->addr;
    p->flags = a->flags;
    t->prl_count++;
    rcu_assign_pointer(t->prl, p);
    + p = NULL;
    out:
    spin_unlock(&ipip6_prl_lock);
    + kfree(p);
    return err;
    }


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