Revert "wifi: wilc1000: convert list management to RCU"

This reverts commit f236464f1db7bea80075e6e31ac70dc6eb80547f

Commit f236464f1db7 ("wifi: wilc1000: convert list management to RCU")
replaced SRCU with RCU, aiming to simplify RCU usage in the driver. No
documentation or commit history hinted about why SRCU has been preferred
in original design, so it has been assumed to be safe to do this
conversion.
Unfortunately, some static analyzers raised warnings, confirmed by runtime
checker, not long after the merge. At least three different issues arose
when switching to RCU:
- wilc_wlan_txq_filter_dup_tcp_ack is executed in a RCU read critical
  section yet calls wait_for_completion_timeout
- wilc_wfi_init_mon_interface calls kmalloc and register_netdevice while
  manipulating a vif retrieved from vif list
- set_channel sends command to chip (and so, also waits for a completion)
  while holding a vif retrieved from vif list (so, in RCU read critical
  section)

Some of those issues are not trivial to fix and would need bigger driver
rework. Fix those issues by reverting the SRCU to RCU conversion commit

Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Closes: https://lore.kernel.org/linux-wireless/3b46ec7c-baee-49fd-b760-3bc12fb12eaf@moroto.mountain/
Fixes: f236464f1db7 ("wifi: wilc1000: convert list management to RCU")
Signed-off-by: Alexis Lothoré <alexis.lothore@bootlin.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://msgid.link/20240528-wilc_revert_srcu_to_rcu-v1-1-bce096e0798c@bootlin.com

1 files changed, 9 insertions, 6 deletions

diff --git a/drivers/net/wireless/microchip/wilc1000/hif.c b/drivers/net/wireless/microchip/wilc1000/hif.c
index 919de6ffb821..3925ca653e80 100644
--- a/drivers/net/wireless/microchip/wilc1000/hif.c
+++ b/drivers/net/wireless/microchip/wilc1000/hif.c
@@ -1570,11 +1570,12 @@ void wilc_network_info_received(struct wilc *wilc, u8 *buffer, u32 length)
 	struct host_if_drv *hif_drv;
 	struct host_if_msg *msg;
 	struct wilc_vif *vif;
+	int srcu_idx;
 	int result;
 	int id;
 
 	id = get_unaligned_le32(&buffer[length - 4]);
-	rcu_read_lock();
+	srcu_idx = srcu_read_lock(&wilc->srcu);
 	vif = wilc_get_vif_from_idx(wilc, id);
 	if (!vif)
 		goto out;
@@ -1606,7 +1607,7 @@ void wilc_network_info_received(struct wilc *wilc, u8 *buffer, u32 length)
 		kfree(msg);
 	}
 out:
-	rcu_read_unlock();
+	srcu_read_unlock(&wilc->srcu, srcu_idx);
 }
 
 void wilc_gnrl_async_info_received(struct wilc *wilc, u8 *buffer, u32 length)
@@ -1614,13 +1615,14 @@ void wilc_gnrl_async_info_received(struct wilc *wilc, u8 *buffer, u32 length)
 	struct host_if_drv *hif_drv;
 	struct host_if_msg *msg;
 	struct wilc_vif *vif;
+	int srcu_idx;
 	int result;
 	int id;
 
 	mutex_lock(&wilc->deinit_lock);
 
 	id = get_unaligned_le32(&buffer[length - 4]);
-	rcu_read_lock();
+	srcu_idx = srcu_read_lock(&wilc->srcu);
 	vif = wilc_get_vif_from_idx(wilc, id);
 	if (!vif)
 		goto out;
@@ -1647,7 +1649,7 @@ void wilc_gnrl_async_info_received(struct wilc *wilc, u8 *buffer, u32 length)
 		kfree(msg);
 	}
 out:
-	rcu_read_unlock();
+	srcu_read_unlock(&wilc->srcu, srcu_idx);
 	mutex_unlock(&wilc->deinit_lock);
 }
 
@@ -1655,11 +1657,12 @@ void wilc_scan_complete_received(struct wilc *wilc, u8 *buffer, u32 length)
 {
 	struct host_if_drv *hif_drv;
 	struct wilc_vif *vif;
+	int srcu_idx;
 	int result;
 	int id;
 
 	id = get_unaligned_le32(&buffer[length - 4]);
-	rcu_read_lock();
+	srcu_idx = srcu_read_lock(&wilc->srcu);
 	vif = wilc_get_vif_from_idx(wilc, id);
 	if (!vif)
 		goto out;
@@ -1684,7 +1687,7 @@ void wilc_scan_complete_received(struct wilc *wilc, u8 *buffer, u32 length)
 		}
 	}
 out:
-	rcu_read_unlock();
+	srcu_read_unlock(&wilc->srcu, srcu_idx);
 }
 
 int wilc_remain_on_channel(struct wilc_vif *vif, u64 cookie, u16 chan,