Re: [PATCH] net: xen-netbank: hash.c: Use built-in RCU list checking
From: Wei Liu <wei.liu@kernel.org>
Date: 2020-01-15 13:57:42
Also in:
linux-kernel-mentees, lkml, xen-devel
Thanks for the patch. There is a typo in the subject line. It should say xen-netback, not xen-netbank. On Wed, Jan 15, 2020 at 06:11:28PM +0530, madhuparnabhowmik04@gmail.com wrote:
quoted hunk ↗ jump to hunk
From: Madhuparna Bhowmik <redacted> list_for_each_entry_rcu has built-in RCU and lock checking. Pass cond argument to list_for_each_entry_rcu. Signed-off-by: Madhuparna Bhowmik <redacted> --- drivers/net/xen-netback/hash.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)diff --git a/drivers/net/xen-netback/hash.c b/drivers/net/xen-netback/hash.c index 10d580c3dea3..30709bc9d170 100644 --- a/drivers/net/xen-netback/hash.c +++ b/drivers/net/xen-netback/hash.c@@ -51,7 +51,8 @@ static void xenvif_add_hash(struct xenvif *vif, const u8 *tag, found = false; oldest = NULL; - list_for_each_entry_rcu(entry, &vif->hash.cache.list, link) { + list_for_each_entry_rcu(entry, &vif->hash.cache.list, link, + lockdep_is_held(&vif->hash.cache.lock)) {
There are probably too many tabs here. Indentation looks wrong. The surrounding code makes it pretty clear that the lock is already held by the time list_for_each_entry_rcu is called, yet the checking involved in lockdep_is_held is not trivial, so I'm afraid I don't consider this a strict improvement over the existing code. If there is something I misunderstood, let me know. Wei.
quoted hunk ↗ jump to hunk
/* Make sure we don't add duplicate entries */ if (entry->len == len && memcmp(entry->tag, tag, len) == 0)@@ -102,7 +103,8 @@ static void xenvif_flush_hash(struct xenvif *vif) spin_lock_irqsave(&vif->hash.cache.lock, flags); - list_for_each_entry_rcu(entry, &vif->hash.cache.list, link) { + list_for_each_entry_rcu(entry, &vif->hash.cache.list, link, + lockdep_is_held(&vif->hash.cache.lock)) { list_del_rcu(&entry->link); vif->hash.cache.count--; kfree_rcu(entry, rcu);-- 2.17.1