netdev - [PATCH v2] net: atm: Add annotation for lec_priv_walk() and lec_seq

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Date:   Wed, 29 Apr 2020 15:58:46 +0100
From:   Jules Irenge <jbi.octave@...il.com>
To:     linux-kernel@...r.kernel.org
Cc:     "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        netdev@...r.kernel.org (open list:NETWORKING [GENERAL])
Subject: [PATCH v2] net: atm: Add annotation for lec_priv_walk() and lec_seq_stop()

Sparse reports a warning at lec_priv_walk() and lec_seq_stop()

warning: context imbalance in lec_priv_walk() - unexpected unlock
warning: context imbalance in lec_seq_stop() - unexpected unlock

The root cause is the missing annotation at lec_priv_walk()
	and lec_seq_stop()
To fix this, __acquire() and __release() annotations
are added in case conditions are not met.
This only instruct Sparse to shutdown the warning

Add the  __acquire(&priv->lec_arp_lock)
Add __release(&priv->lec_arp_lock) annotation
Add __releases(&state->locked->lec_arp_lock) annotation
Add  __release(&state->locked->lec_arp_lock) annotation

Signed-off-by: Jules Irenge <jbi.octave@...il.com>
---
Changes since v2 
- merge patch No 6 and No 4 into one

 net/atm/lec.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/net/atm/lec.c b/net/atm/lec.c
index 25fa3a7b72bd..7947abb17af2 100644
--- a/net/atm/lec.c
+++ b/net/atm/lec.c
@@ -886,12 +886,18 @@ static void *lec_priv_walk(struct lec_state *state, loff_t *l,
 	if (!state->locked) {
 		state->locked = priv;
 		spin_lock_irqsave(&priv->lec_arp_lock, state->flags);
+	} else {
+		/* annotation for sparse */
+		__acquire(&priv->lec_arp_lock);
 	}
 	if (!lec_arp_walk(state, l, priv) && !lec_misc_walk(state, l, priv)) {
 		spin_unlock_irqrestore(&priv->lec_arp_lock, state->flags);
 		state->locked = NULL;
 		/* Partial state reset for the next time we get called */
 		state->arp_table = state->misc_table = 0;
+	} else {
+		/* annotation for sparse */
+		__release(&priv->lec_arp_lock);
 	}
 	return state->locked;
 }
@@ -940,6 +946,7 @@ static void *lec_seq_start(struct seq_file *seq, loff_t *pos)
 }
 
 static void lec_seq_stop(struct seq_file *seq, void *v)
+	__releases(&state->locked->lec_arp_lock)
 {
 	struct lec_state *state = seq->private;
 
@@ -947,6 +954,9 @@ static void lec_seq_stop(struct seq_file *seq, void *v)
 		spin_unlock_irqrestore(&state->locked->lec_arp_lock,
 				       state->flags);
 		dev_put(state->dev);
+	} else {
+		/* annotation for sparse */
+		__release(&state->locked->lec_arp_lock);
 	}
 }
 
-- 
2.25.3