From: Wei Liu <wei.liu@kernel.org>
To: madhuparnabhowmik04@gmail.com
Cc: wei.liu@kernel.org, paulmck@kernel.org, paul@xen.org,
netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
joel@joelfernandes.org, xen-devel@lists.xenproject.org,
linux-kernel-mentees@lists.linuxfoundation.org,
davem@davemloft.net
Subject: Re: [Linux-kernel-mentees] [PATCH] net: xen-netbank: hash.c: Use built-in RCU list checking
Date: Wed, 15 Jan 2020 13:56:31 +0000 [thread overview]
Message-ID: <20200115135631.edr2nrfkycppxcku@debian> (raw)
In-Reply-To: <20200115124129.5684-1-madhuparnabhowmik04@gmail.com>
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:
> From: Madhuparna Bhowmik <madhuparnabhowmik04@gmail.com>
>
> 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 <madhuparnabhowmik04@gmail.com>
> ---
> 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.
> /* 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
>
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next prev parent reply other threads:[~2020-01-15 13:56 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-15 12:41 [Linux-kernel-mentees] [PATCH] net: xen-netbank: hash.c: Use built-in RCU list checking madhuparnabhowmik04
2020-01-15 13:56 ` Wei Liu [this message]
2020-01-15 14:06 ` Madhuparna Bhowmik
2020-01-15 15:04 ` Wei Liu
2020-01-15 15:46 ` Madhuparna Bhowmik
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