printk ratelimiting rewrite

All ratelimit user use same jiffies and burst params, so some messages
(callbacks) will be lost.

For example:
a call printk_ratelimit(5 * HZ, 1)
b call printk_ratelimit(5 * HZ, 1) before the 5*HZ timeout of a, then b will
will be supressed.

- rewrite __ratelimit, and use a ratelimit_state as parameter.  Thanks for
  hints from andrew.

- Add WARN_ON_RATELIMIT, update rcupreempt.h

- remove __printk_ratelimit

- use __ratelimit in net_ratelimit

Signed-off-by: Dave Young <hidave.darkstar@gmail.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: "Paul E. McKenney" <paulmck@us.ibm.com>
Cc: Dave Young <hidave.darkstar@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/include/asm-generic/bug.h b/include/asm-generic/bug.h
index a346e74..a3f738c 100644 (file)
--- a/include/asm-generic/bug.h
+++ b/include/asm-generic/bug.h
@@ -97,6 +97,9 @@ extern void warn_slowpath(const char *file, const int line,
        unlikely(__ret_warn_once);                              \
 })
 
+#define WARN_ON_RATELIMIT(condition, state)                    \
+               WARN_ON((condition) && __ratelimit(state))
+
 #ifdef CONFIG_SMP
 # define WARN_ON_SMP(x)                        WARN_ON(x)
 #else

diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index 5c4b125..fdbbf72 100644 (file)
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -15,6 +15,7 @@
 #include <linux/bitops.h>
 #include <linux/log2.h>
 #include <linux/typecheck.h>
+#include <linux/ratelimit.h>
 #include <asm/byteorder.h>
 #include <asm/bug.h>
 
@@ -189,11 +190,8 @@ asmlinkage int vprintk(const char *fmt, va_list args)
 asmlinkage int printk(const char * fmt, ...)
        __attribute__ ((format (printf, 1, 2))) __cold;
 
-extern int printk_ratelimit_jiffies;
-extern int printk_ratelimit_burst;
+extern struct ratelimit_state printk_ratelimit_state;
 extern int printk_ratelimit(void);
-extern int __ratelimit(int ratelimit_jiffies, int ratelimit_burst);
-extern int __printk_ratelimit(int ratelimit_jiffies, int ratelimit_burst);
 extern bool printk_timed_ratelimit(unsigned long *caller_jiffies,
                                   unsigned int interval_msec);
 #else
@@ -204,8 +202,6 @@ static inline int printk(const char *s, ...)
        __attribute__ ((format (printf, 1, 2)));
 static inline int __cold printk(const char *s, ...) { return 0; }
 static inline int printk_ratelimit(void) { return 0; }
-static inline int __printk_ratelimit(int ratelimit_jiffies, \
-                                    int ratelimit_burst) { return 0; }
 static inline bool printk_timed_ratelimit(unsigned long *caller_jiffies, \
                                          unsigned int interval_msec)   \
                { return false; }

diff --git a/include/linux/net.h b/include/linux/net.h
index 2f999fb..4a9a30f 100644 (file)
--- a/include/linux/net.h
+++ b/include/linux/net.h
@@ -351,8 +351,7 @@ static const struct proto_ops name##_ops = {                        \
 
 #ifdef CONFIG_SYSCTL
 #include <linux/sysctl.h>
-extern int net_msg_cost;
-extern int net_msg_burst;
+extern struct ratelimit_state net_ratelimit_state;
 #endif
 
 #endif /* __KERNEL__ */

diff --git a/include/linux/ratelimit.h b/include/linux/ratelimit.h
new file mode 100644 (file)
index 0000000..18a5b9b
--- /dev/null
+++ b/include/linux/ratelimit.h
@@ -0,0 +1,27 @@
+#ifndef _LINUX_RATELIMIT_H
+#define _LINUX_RATELIMIT_H
+#include <linux/param.h>
+
+#define DEFAULT_RATELIMIT_INTERVAL (5 * HZ)
+#define DEFAULT_RATELIMIT_BURST 10
+
+struct ratelimit_state {
+       int interval;
+       int burst;
+       int printed;
+       int missed;
+       unsigned long begin;
+};
+
+#define DEFINE_RATELIMIT_STATE(name, interval, burst)          \
+               struct ratelimit_state name = {interval, burst,}
+
+extern int __ratelimit(struct ratelimit_state *rs);
+
+static inline int ratelimit(void)
+{
+       static DEFINE_RATELIMIT_STATE(rs, DEFAULT_RATELIMIT_INTERVAL,
+                                       DEFAULT_RATELIMIT_BURST);
+       return __ratelimit(&rs);
+}
+#endif

diff --git a/include/linux/rcupreempt.h b/include/linux/rcupreempt.h
index f04b64e..0967f03 100644 (file)
--- a/include/linux/rcupreempt.h
+++ b/include/linux/rcupreempt.h
@@ -115,16 +115,21 @@ DECLARE_PER_CPU(struct rcu_dyntick_sched, rcu_dyntick_sched);
 
 static inline void rcu_enter_nohz(void)
 {
+       static DEFINE_RATELIMIT_STATE(rs, 10 * HZ, 1);
+
        smp_mb(); /* CPUs seeing ++ must see prior RCU read-side crit sects */
        __get_cpu_var(rcu_dyntick_sched).dynticks++;
-       WARN_ON(__get_cpu_var(rcu_dyntick_sched).dynticks & 0x1);
+       WARN_ON_RATELIMIT(__get_cpu_var(rcu_dyntick_sched).dynticks & 0x1, &rs);
 }
 
 static inline void rcu_exit_nohz(void)
 {
+       static DEFINE_RATELIMIT_STATE(rs, 10 * HZ, 1);
+
        smp_mb(); /* CPUs seeing ++ must see later RCU read-side crit sects */
        __get_cpu_var(rcu_dyntick_sched).dynticks++;
-       WARN_ON(!(__get_cpu_var(rcu_dyntick_sched).dynticks & 0x1));
+       WARN_ON_RATELIMIT(!(__get_cpu_var(rcu_dyntick_sched).dynticks & 0x1),
+                               &rs);
 }
 
 #else /* CONFIG_NO_HZ */

diff --git a/kernel/printk.c b/kernel/printk.c
index 3f7a2a9..a7f7559 100644 (file)
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -1308,6 +1308,8 @@ void tty_write_message(struct tty_struct *tty, char *msg)
 }
 
 #if defined CONFIG_PRINTK
+
+DEFINE_RATELIMIT_STATE(printk_ratelimit_state, 5 * HZ, 10);
 /*
  * printk rate limiting, lifted from the networking subsystem.
  *
@@ -1315,22 +1317,9 @@ void tty_write_message(struct tty_struct *tty, char *msg)
  * every printk_ratelimit_jiffies to make a denial-of-service
  * attack impossible.
  */
-int __printk_ratelimit(int ratelimit_jiffies, int ratelimit_burst)
-{
-       return __ratelimit(ratelimit_jiffies, ratelimit_burst);
-}
-EXPORT_SYMBOL(__printk_ratelimit);
-
-/* minimum time in jiffies between messages */
-int printk_ratelimit_jiffies = 5 * HZ;
-
-/* number of messages we send before ratelimiting */
-int printk_ratelimit_burst = 10;
-
 int printk_ratelimit(void)
 {
-       return __printk_ratelimit(printk_ratelimit_jiffies,
-                               printk_ratelimit_burst);
+       return __ratelimit(&printk_ratelimit_state);
 }
 EXPORT_SYMBOL(printk_ratelimit);
 

diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 1a8299d..35a50db 100644 (file)
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -624,7 +624,7 @@ static struct ctl_table kern_table[] = {
        {
                .ctl_name       = KERN_PRINTK_RATELIMIT,
                .procname       = "printk_ratelimit",
-               .data           = &printk_ratelimit_jiffies,
+               .data           = &printk_ratelimit_state.interval,
                .maxlen         = sizeof(int),
                .mode           = 0644,
                .proc_handler   = &proc_dointvec_jiffies,
@@ -633,7 +633,7 @@ static struct ctl_table kern_table[] = {
        {
                .ctl_name       = KERN_PRINTK_RATELIMIT_BURST,
                .procname       = "printk_ratelimit_burst",
-               .data           = &printk_ratelimit_burst,
+               .data           = &printk_ratelimit_state.burst,
                .maxlen         = sizeof(int),
                .mode           = 0644,
                .proc_handler   = &proc_dointvec,

diff --git a/lib/ratelimit.c b/lib/ratelimit.c
index 485e304..3513667 100644 (file)
--- a/lib/ratelimit.c
+++ b/lib/ratelimit.c
@@ -3,6 +3,9 @@
  *
  * Isolated from kernel/printk.c by Dave Young <hidave.darkstar@gmail.com>
  *
+ * 2008-05-01 rewrite the function and use a ratelimit_state data struct as
+ * parameter. Now every user can use their own standalone ratelimit_state.
+ *
  * This file is released under the GPLv2.
  *
  */
@@ -11,41 +14,43 @@
 #include <linux/jiffies.h>
 #include <linux/module.h>
 
+static DEFINE_SPINLOCK(ratelimit_lock);
+static unsigned long flags;
+
 /*
  * __ratelimit - rate limiting
- * @ratelimit_jiffies: minimum time in jiffies between two callbacks
- * @ratelimit_burst: number of callbacks we do before ratelimiting
+ * @rs: ratelimit_state data
  *
- * This enforces a rate limit: not more than @ratelimit_burst callbacks
- * in every ratelimit_jiffies
+ * This enforces a rate limit: not more than @rs->ratelimit_burst callbacks
+ * in every @rs->ratelimit_jiffies
  */
-int __ratelimit(int ratelimit_jiffies, int ratelimit_burst)
+int __ratelimit(struct ratelimit_state *rs)
 {
-       static DEFINE_SPINLOCK(ratelimit_lock);
-       static unsigned toks = 10 * 5 * HZ;
-       static unsigned long last_msg;
-       static int missed;
-       unsigned long flags;
-       unsigned long now = jiffies;
+       if (!rs->interval)
+               return 1;
 
        spin_lock_irqsave(&ratelimit_lock, flags);
-       toks += now - last_msg;
-       last_msg = now;
-       if (toks > (ratelimit_burst * ratelimit_jiffies))
-               toks = ratelimit_burst * ratelimit_jiffies;
-       if (toks >= ratelimit_jiffies) {
-               int lost = missed;
+       if (!rs->begin)
+               rs->begin = jiffies;
 
-               missed = 0;
-               toks -= ratelimit_jiffies;
-               spin_unlock_irqrestore(&ratelimit_lock, flags);
-               if (lost)
-                       printk(KERN_WARNING "%s: %d messages suppressed\n",
-                               __func__, lost);
-               return 1;
+       if (time_is_before_jiffies(rs->begin + rs->interval)) {
+               if (rs->missed)
+                       printk(KERN_WARNING "%s: %d callbacks suppressed\n",
+                               __func__, rs->missed);
+               rs->begin = 0;
+               rs->printed = 0;
+               rs->missed = 0;
        }
-       missed++;
+       if (rs->burst && rs->burst > rs->printed)
+               goto print;
+
+       rs->missed++;
        spin_unlock_irqrestore(&ratelimit_lock, flags);
        return 0;
+
+print:
+       rs->printed++;
+       spin_unlock_irqrestore(&ratelimit_lock, flags);
+       return 1;
 }
 EXPORT_SYMBOL(__ratelimit);

diff --git a/net/core/sysctl_net_core.c b/net/core/sysctl_net_core.c
index a570e2a..f686467 100644 (file)
--- a/net/core/sysctl_net_core.c
+++ b/net/core/sysctl_net_core.c
@@ -67,7 +67,7 @@ static struct ctl_table net_core_table[] = {
        {
                .ctl_name       = NET_CORE_MSG_COST,
                .procname       = "message_cost",
-               .data           = &net_msg_cost,
+               .data           = &net_ratelimit_state.interval,
                .maxlen         = sizeof(int),
                .mode           = 0644,
                .proc_handler   = &proc_dointvec_jiffies,
@@ -76,7 +76,7 @@ static struct ctl_table net_core_table[] = {
        {
                .ctl_name       = NET_CORE_MSG_BURST,
                .procname       = "message_burst",
-               .data           = &net_msg_burst,
+               .data           = &net_ratelimit_state.burst,
                .maxlen         = sizeof(int),
                .mode           = 0644,
                .proc_handler   = &proc_dointvec,

diff --git a/net/core/utils.c b/net/core/utils.c
index 8031eb5..72e0ebe 100644 (file)
--- a/net/core/utils.c
+++ b/net/core/utils.c
@@ -31,17 +31,16 @@
 #include <asm/system.h>
 #include <asm/uaccess.h>
 
-int net_msg_cost __read_mostly = 5*HZ;
-int net_msg_burst __read_mostly = 10;
 int net_msg_warn __read_mostly = 1;
 EXPORT_SYMBOL(net_msg_warn);
 
+DEFINE_RATELIMIT_STATE(net_ratelimit_state, 5 * HZ, 10);
 /*
  * All net warning printk()s should be guarded by this function.
  */
 int net_ratelimit(void)
 {
-       return __printk_ratelimit(net_msg_cost, net_msg_burst);
+       return __ratelimit(&net_ratelimit_state);
 }
 EXPORT_SYMBOL(net_ratelimit);