From e64a348dc148af41cec266b2143305a2d0228ee7 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Tue, 25 Mar 2025 15:32:54 -0700 Subject: [PATCH] ratelimit: Avoid jiffies=0 special case The ___ratelimit() function special-cases the jiffies-counter value of zero as "uninitialized". This works well on 64-bit systems, where the jiffies counter is not going to return to zero for more than half a billion years on systems with HZ=1000, but similar 32-bit systems take less than 50 days to wrap the jiffies counter. And although the consequences of wrapping the jiffies counter seem to be limited to minor confusion on the duration of the rate-limiting interval that happens to end at time zero, it is almost no work to avoid this confusion. Therefore, introduce a RATELIMIT_INITIALIZED bit to the ratelimit_state structure's ->flags field so that a ->begin value of zero is no longer special. Link: https://lore.kernel.org/all/fbe93a52-365e-47fe-93a4-44a44547d601@paulmck-laptop/ Link: https://lore.kernel.org/all/20250423115409.3425-1-spasswolf@web.de/ Signed-off-by: Paul E. McKenney Reviewed-by: Petr Mladek Cc: Andrew Morton Cc: Kuniyuki Iwashima Cc: Mateusz Guzik Cc: Steven Rostedt Cc: John Ogness Cc: Sergey Senozhatsky --- include/linux/ratelimit.h | 2 +- include/linux/ratelimit_types.h | 1 + lib/ratelimit.c | 4 +++- 3 files changed, 5 insertions(+), 2 deletions(-) diff --git a/include/linux/ratelimit.h b/include/linux/ratelimit.h index c78b92b3e5cd8..adfec24061d16 100644 --- a/include/linux/ratelimit.h +++ b/include/linux/ratelimit.h @@ -43,7 +43,7 @@ static inline void ratelimit_state_reset_interval(struct ratelimit_state *rs, in raw_spin_lock_irqsave(&rs->lock, flags); rs->interval = interval_init; - rs->begin = 0; + rs->flags &= ~RATELIMIT_INITIALIZED; rs->printed = 0; ratelimit_state_reset_miss(rs); raw_spin_unlock_irqrestore(&rs->lock, flags); diff --git a/include/linux/ratelimit_types.h b/include/linux/ratelimit_types.h index d21fe82b67f67..ef6711b6b229f 100644 --- a/include/linux/ratelimit_types.h +++ b/include/linux/ratelimit_types.h @@ -11,6 +11,7 @@ /* issue num suppressed message on exit */ #define RATELIMIT_MSG_ON_RELEASE BIT(0) +#define RATELIMIT_INITIALIZED BIT(1) struct ratelimit_state { raw_spinlock_t lock; /* protect the state */ diff --git a/lib/ratelimit.c b/lib/ratelimit.c index 19ad3cdbd1711..bd6e3b429e333 100644 --- a/lib/ratelimit.c +++ b/lib/ratelimit.c @@ -49,8 +49,10 @@ int ___ratelimit(struct ratelimit_state *rs, const char *func) return 0; } - if (!rs->begin) + if (!(rs->flags & RATELIMIT_INITIALIZED)) { rs->begin = jiffies; + rs->flags |= RATELIMIT_INITIALIZED; + } if (time_is_before_jiffies(rs->begin + interval)) { int m = ratelimit_state_reset_miss(rs); -- 2.47.2