[PATCH] connector/cn_proc: cn_netlink_has_listeners replaces proc_event_num_listeners

From: Keqi Wang
Date: Sun Feb 04 2024 - 03:24:42 EST

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It is not accurate to reset proc_event_num_listeners according to
cn_netlink_send_mult() return value -ESRCH.

In the case of stress-ng netlink-proc, -ESRCH will always be returned,
because netlink_broadcast_filtered will return -ESRCH,
which may cause stress-ng netlink-proc performance degradation.

proc_event_num_listeners cannot accurately reflect whether
the listener exists, so add cn_netlink_has_listeners() functon
and use that instead of proc_event_num_listeners.

Reported-by: kernel test robot <oliver.sang@xxxxxxxxx>
Closes: https://lore.kernel.org/oe-lkp/202401112259.b23a1567-oliver.sang@xxxxxxxxx
Fixes: c46bfba1337d ("connector: Fix proc_event_num_listeners count not cleared")
Signed-off-by: Keqi Wang <wangkeqi_chris@xxxxxxx>
---
drivers/connector/cn_proc.c | 46 +++++++++++++++++------------------
drivers/connector/connector.c | 9 +++++++
include/linux/connector.h | 2 ++
3 files changed, 34 insertions(+), 23 deletions(-)

diff --git a/drivers/connector/cn_proc.c b/drivers/connector/cn_proc.c
index 3d5e6d705..5d0339ee7 100644
--- a/drivers/connector/cn_proc.c
+++ b/drivers/connector/cn_proc.c
@@ -36,7 +36,6 @@ static inline struct cn_msg *buffer_to_cn_msg(__u8 *buffer)
return (struct cn_msg *)(buffer + 4);
}

-static atomic_t proc_event_num_listeners = ATOMIC_INIT(0);
static struct cb_id cn_proc_event_id = { CN_IDX_PROC, CN_VAL_PROC };

/* local_event.count is used as the sequence number of the netlink message */
@@ -85,6 +84,16 @@ static int cn_filter(struct sock *dsk, struct sk_buff *skb, void *data)
return 1;
}

+static int cn_netlink_has_listeners(void)
+{
+ struct sock *sk = cn_cdev_nls_get();
+
+ if (sk)
+ return netlink_has_listeners(sk, CN_IDX_PROC);
+ else
+ return 0;
+}
+
static inline void send_msg(struct cn_msg *msg)
{
__u32 filter_data[2];
@@ -108,9 +117,8 @@ static inline void send_msg(struct cn_msg *msg)
filter_data[1] = 0;
}

- if (cn_netlink_send_mult(msg, msg->len, 0, CN_IDX_PROC, GFP_NOWAIT,
- cn_filter, (void *)filter_data) == -ESRCH)
- atomic_set(&proc_event_num_listeners, 0);
+ cn_netlink_send_mult(msg, msg->len, 0, CN_IDX_PROC, GFP_NOWAIT,
+ cn_filter, (void *)filter_data);

local_unlock(&local_event.lock);
}
@@ -122,7 +130,7 @@ void proc_fork_connector(struct task_struct *task)
__u8 buffer[CN_PROC_MSG_SIZE] __aligned(8);
struct task_struct *parent;

- if (atomic_read(&proc_event_num_listeners) < 1)
+ if (!cn_netlink_has_listeners())
return;

msg = buffer_to_cn_msg(buffer);
@@ -151,7 +159,7 @@ void proc_exec_connector(struct task_struct *task)
struct proc_event *ev;
__u8 buffer[CN_PROC_MSG_SIZE] __aligned(8);

- if (atomic_read(&proc_event_num_listeners) < 1)
+ if (!cn_netlink_has_listeners())
return;

msg = buffer_to_cn_msg(buffer);
@@ -176,7 +184,7 @@ void proc_id_connector(struct task_struct *task, int which_id)
__u8 buffer[CN_PROC_MSG_SIZE] __aligned(8);
const struct cred *cred;

- if (atomic_read(&proc_event_num_listeners) < 1)
+ if (!cn_netlink_has_listeners())
return;

msg = buffer_to_cn_msg(buffer);
@@ -213,7 +221,7 @@ void proc_sid_connector(struct task_struct *task)
struct proc_event *ev;
__u8 buffer[CN_PROC_MSG_SIZE] __aligned(8);

- if (atomic_read(&proc_event_num_listeners) < 1)
+ if (!cn_netlink_has_listeners())
return;

msg = buffer_to_cn_msg(buffer);
@@ -237,7 +245,7 @@ void proc_ptrace_connector(struct task_struct *task, int ptrace_id)
struct proc_event *ev;
__u8 buffer[CN_PROC_MSG_SIZE] __aligned(8);

- if (atomic_read(&proc_event_num_listeners) < 1)
+ if (!cn_netlink_has_listeners())
return;

msg = buffer_to_cn_msg(buffer);
@@ -269,7 +277,7 @@ void proc_comm_connector(struct task_struct *task)
struct proc_event *ev;
__u8 buffer[CN_PROC_MSG_SIZE] __aligned(8);

- if (atomic_read(&proc_event_num_listeners) < 1)
+ if (!cn_netlink_has_listeners())
return;

msg = buffer_to_cn_msg(buffer);
@@ -295,7 +303,7 @@ void proc_coredump_connector(struct task_struct *task)
struct task_struct *parent;
__u8 buffer[CN_PROC_MSG_SIZE] __aligned(8);

- if (atomic_read(&proc_event_num_listeners) < 1)
+ if (!cn_netlink_has_listeners())
return;

msg = buffer_to_cn_msg(buffer);
@@ -328,7 +336,7 @@ void proc_exit_connector(struct task_struct *task)
struct task_struct *parent;
__u8 buffer[CN_PROC_MSG_SIZE] __aligned(8);

- if (atomic_read(&proc_event_num_listeners) < 1)
+ if (!cn_netlink_has_listeners())
return;

msg = buffer_to_cn_msg(buffer);
@@ -370,7 +378,7 @@ static void cn_proc_ack(int err, int rcvd_seq, int rcvd_ack)
struct proc_event *ev;
__u8 buffer[CN_PROC_MSG_SIZE] __aligned(8);

- if (atomic_read(&proc_event_num_listeners) < 1)
+ if (!cn_netlink_has_listeners())
return;

msg = buffer_to_cn_msg(buffer);
@@ -396,10 +404,10 @@ static void cn_proc_ack(int err, int rcvd_seq, int rcvd_ack)
static void cn_proc_mcast_ctl(struct cn_msg *msg,
struct netlink_skb_parms *nsp)
{
- enum proc_cn_mcast_op mc_op = 0, prev_mc_op = 0;
+ enum proc_cn_mcast_op mc_op = 0;
struct proc_input *pinput = NULL;
enum proc_cn_event ev_type = 0;
- int err = 0, initial = 0;
+ int err = 0;
struct sock *sk = NULL;

/*
@@ -436,10 +444,6 @@ static void cn_proc_mcast_ctl(struct cn_msg *msg,
err = ENOMEM;
goto out;
}
- initial = 1;
- } else {
- prev_mc_op =
- ((struct proc_input *)(sk->sk_user_data))->mcast_op;
}
((struct proc_input *)(sk->sk_user_data))->event_type =
ev_type;
@@ -448,12 +452,8 @@ static void cn_proc_mcast_ctl(struct cn_msg *msg,

switch (mc_op) {
case PROC_CN_MCAST_LISTEN:
- if (initial || (prev_mc_op != PROC_CN_MCAST_LISTEN))
- atomic_inc(&proc_event_num_listeners);
break;
case PROC_CN_MCAST_IGNORE:
- if (!initial && (prev_mc_op != PROC_CN_MCAST_IGNORE))
- atomic_dec(&proc_event_num_listeners);
((struct proc_input *)(sk->sk_user_data))->event_type =
PROC_EVENT_NONE;
break;
diff --git a/drivers/connector/connector.c b/drivers/connector/connector.c
index 7f7b94f61..540249d6d 100644
--- a/drivers/connector/connector.c
+++ b/drivers/connector/connector.c
@@ -129,6 +129,15 @@ int cn_netlink_send(struct cn_msg *msg, u32 portid, u32 __group,
}
EXPORT_SYMBOL_GPL(cn_netlink_send);

+struct sock *cn_cdev_nls_get(void)
+{
+ if (cn_already_initialized == 1)
+ return cdev.nls;
+ else
+ return NULL;
+}
+EXPORT_SYMBOL_GPL(cn_cdev_nls_get);
+
/*
* Callback helper - queues work and setup destructor for given data.
*/
diff --git a/include/linux/connector.h b/include/linux/connector.h
index cec2d99ae..ca4d0cca7 100644
--- a/include/linux/connector.h
+++ b/include/linux/connector.h
@@ -127,6 +127,8 @@ int cn_netlink_send_mult(struct cn_msg *msg, u16 len, u32 portid,
*/
int cn_netlink_send(struct cn_msg *msg, u32 portid, u32 group, gfp_t gfp_mask);

+struct sock *cn_cdev_nls_get(void);
+
int cn_queue_add_callback(struct cn_queue_dev *dev, const char *name,
const struct cb_id *id,
void (*callback)(struct cn_msg *, struct netlink_skb_parms *));
--
2.27.0

Next message: Xu Yilun: "Re: [PATCH 1/3] fpga: xilinx-spi: extract a common driver core"
Previous message: Ywe Caerlyn: "@ X (was fair source)"
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