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 oops_in_progress is set, 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. Signed-off-by: Breno Leitao <[email protected]> --- drivers/net/netconsole.c | 31 +++++++++++++++++++++++++++++++ 1 file changed, 31 insertions(+) diff --git a/drivers/net/netconsole.c b/drivers/net/netconsole.c index b358e5c367351..2ad514afa2b89 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 <[email protected]>"); MODULE_DESCRIPTION("Console driver for network interfaces"); @@ -175,6 +176,7 @@ struct netcons_userdata { * @sysdata: Cached, formatted string of append * @sysdata_fields: Sysdata features enabled. * @msgcounter: Message sent counter. + * @ratelimit: Opaque structure to ratelimit messages * @stats: Packet send stats for the target. Used for debugging. * @state: State of the target. * Visible from userspace (read-write). @@ -219,6 +221,7 @@ struct netconsole_target { u32 sysdata_fields; /* protected by target_list_lock */ u32 msgcounter; + struct ratelimit_state ratelimit; #endif struct netconsole_target_stats stats; enum target_state state; @@ -282,6 +285,21 @@ 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); + 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 (oops_in_progress) + return false; + + return !__ratelimit(&nt->ratelimit); +} + #else /* !CONFIG_NETCONSOLE_DYNAMIC */ static int __init dynamic_netconsole_init(void) @@ -318,6 +336,15 @@ 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. */ @@ -686,6 +713,7 @@ 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); @@ -2482,6 +2510,9 @@ 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
