Give each target a token bucket and consult it once per message in
netconsole_write().
The bucket is created with a zero interval, which struct ratelimit_state
treats as unlimited, and nothing can set a nonzero one yet, so no target
changes behaviour.
Skip the bucket while the kernel is dying, reusing the helper the
oops_only fix added, so a limit configured for steady-state logging
never truncates an oops, BUG() or panic().
The configfs files that expose it come next.
___ratelimit() only trylocks its own raw spinlock, so it is safe with
target_list_lock held and interrupts disabled, and safe from NMI. Set
RATELIMIT_MSG_ON_RELEASE so it does not report the suppressed count
itself, which would printk() from inside the console being serviced.
Reviewed-by: Gustavo Luiz Duarte <gustavold@gmail.com>
Signed-off-by: Breno Leitao <leitao@debian.org>
---
drivers/net/netconsole.c | 37 +++++++++++++++++++++++++++++++++++++
1 file changed, 37 insertions(+)
diff --git a/drivers/net/netconsole.c b/drivers/net/netconsole.c
index 6637b4a16b6c98..3e4495c1cab182 100644
--- a/drivers/net/netconsole.c
+++ b/drivers/net/netconsole.c
@@ -49,6 +49,7 @@
#include <linux/rtnetlink.h>
#include <linux/workqueue.h>
#include <linux/delay.h>
+#include <linux/ratelimit.h>
MODULE_AUTHOR("Matt Mackall <mpm@selenic.com>");
MODULE_DESCRIPTION("Console driver for network interfaces");@@ -196,6 +197,7 @@ struct netcons_userdata {
* @sysdata: Cached, formatted string of append
* @sysdata_fields: Sysdata features enabled.
* @msgcounter: Message sent counter.
+ * @ratelimit: Token bucket used to rate limit messages
* @stats: Packet send stats for the target. Used for debugging.
* @state: State of the target.
* Visible from userspace (read-write).@@ -239,6 +241,8 @@ struct netconsole_target {
u32 sysdata_fields;
/* protected by target_list_lock */
u32 msgcounter;
+ /* carries its own lock, writers hold dynamic_netconsole_mutex */
+ struct ratelimit_state ratelimit;
#endif
struct netconsole_target_stats stats;
enum target_state state;@@ -301,6 +305,26 @@ static void dynamic_netconsole_mutex_unlock(void)
mutex_unlock(&dynamic_netconsole_mutex);
}
+static void netconsole_ratelimit_init(struct netconsole_target *nt)
+{
+ ratelimit_state_init(&nt->ratelimit, 0, DEFAULT_RATELIMIT_BURST);
+ /* The flag keeps ___ratelimit() from reporting the suppressed count
+ * itself, which would printk() from inside the console being
+ * serviced. Nothing calls ratelimit_state_exit(), so the count is
+ * never reported on release either.
+ */
+ ratelimit_set_flags(&nt->ratelimit, RATELIMIT_MSG_ON_RELEASE);
+}
+
+static bool netconsole_ratelimited(struct netconsole_target *nt)
+{
+ /* A limit meant for steady-state logging must not eat a crash dump. */
+ if (netconsole_kernel_dying())
+ return false;
+
+ return !__ratelimit(&nt->ratelimit);
+}
+
#else /* !CONFIG_NETCONSOLE_DYNAMIC */
static int __init dynamic_netconsole_init(void)@@ -337,6 +361,15 @@ static void dynamic_netconsole_mutex_unlock(void)
{
}
+static void netconsole_ratelimit_init(struct netconsole_target *nt)
+{
+}
+
+static bool netconsole_ratelimited(struct netconsole_target *nt)
+{
+ return false;
+}
+
#endif /* CONFIG_NETCONSOLE_DYNAMIC */
/* Check if the target was bound by mac address. */@@ -698,6 +731,7 @@ static struct netconsole_target *alloc_and_init(void)
nt->remote_port = 6666;
eth_broadcast_addr(nt->remote_mac);
nt->state = STATE_DISABLED;
+ netconsole_ratelimit_init(nt);
INIT_WORK(&nt->resume_wq, process_resume_target);
/* Set up the skb pool primitives once; enabling only refills it. */
skb_queue_head_init(&nt->skb_pool);
@@ -2500,6 +2534,9 @@ static void netconsole_write(struct nbcon_write_context *wctxt, bool extended)
!netif_running(nt->np.dev))
continue;
+ if (netconsole_ratelimited(nt))
+ continue;
+
/* If nbcon_enter_unsafe() fails, just return given netconsole
* lost the ownership, and iterating over the targets will not
* be able to re-acquire.
--
2.53.0-Meta