On 2022/9/19 18:27, Dan Carpenter wrote:
On Mon, Sep 19, 2022 at 05:43:33PM +0800, shangxiaojing wrote:
On 2022/9/19 17:11, Greg KH wrote:
On Mon, Sep 19, 2022 at 05:10:56PM +0800, Shang XiaoJing wrote:
Instead of invoking a synchronize_rcu() to free a pointer after a grace
period, we can directly make use of a new API that does the same but in
a more efficient way.
Signed-off-by: Shang XiaoJing <shangxiaojing@xxxxxxxxxx>
---
Changelog:
v3: the first version of the PATCH
v1: v3 resent as v1
v2: use kfree_rcu() instead of kvfree_rcu() for clarity
v4: resend v2 as v4 to avoid versioning confusion
---
drivers/staging/fwserial/fwserial.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/drivers/staging/fwserial/fwserial.c b/drivers/staging/fwserial/fwserial.c
index 81b06d88ed0d..8d2b4ed1f39e 100644
--- a/drivers/staging/fwserial/fwserial.c
+++ b/drivers/staging/fwserial/fwserial.c
@@ -2117,8 +2117,7 @@ static void fwserial_remove_peer(struct fwtty_peer *peer)
if (port)
fwserial_release_port(port, true);
- synchronize_rcu();
- kfree(peer);
+ kfree_rcu(peer);
The kfree_rcu(peer) should be kfree_rcu(peer, rcu), due to the rcu_head
member named rcu in fwtty_peer.
Oh, huh. What happens if you don't pas the "rcu" parameter? I see
there is a similar instance in ext4_apply_quota_options().
kfree_rcu(qname);
We assume for the condition that CONFIG_KASAN_GENERIC does not defined
and system has no pressure (bacause kvfree_call_rcu maintains 3 path):
The input parameter "head" of kvfree_call_rcu will be NULL if we don't
pass the rcu, which will run like:
might_sleep();
synchronize_rcu();
kvfree((void *) func);
instead of:
if (head) {
call_rcu(head, func);
return;
}
where the difference is synchronize_rcu vs call_rcu.
call_rcu() will not block, having a wider range of use compared with
synchronize_rcu().
regards,
dan carpenter
Thanks,
Shang XiaoJing
