From 82dd8419e225958f01708cda8a3fc6c3c5356228 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Sun, 15 Dec 2019 11:38:57 -0800 Subject: rcu: Warn on for_each_leaf_node_cpu_mask() from non-leaf The for_each_leaf_node_cpu_mask() and for_each_leaf_node_possible_cpu() macros must be invoked only on leaf rcu_node structures. Failing to abide by this restriction can result in infinite loops on systems with more than 64 CPUs (or for more than 32 CPUs on 32-bit systems). This commit therefore adds WARN_ON_ONCE() calls to make misuse of these two macros easier to debug. Reported-by: Qian Cai Signed-off-by: Paul E. McKenney --- kernel/rcu/rcu.h | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) (limited to 'kernel/rcu/rcu.h') diff --git a/kernel/rcu/rcu.h b/kernel/rcu/rcu.h index 05f936ed167a..f6ce173e35f6 100644 --- a/kernel/rcu/rcu.h +++ b/kernel/rcu/rcu.h @@ -325,7 +325,8 @@ static inline void rcu_init_levelspread(int *levelspread, const int *levelcnt) * Iterate over all possible CPUs in a leaf RCU node. */ #define for_each_leaf_node_possible_cpu(rnp, cpu) \ - for ((cpu) = cpumask_next((rnp)->grplo - 1, cpu_possible_mask); \ + for (WARN_ON_ONCE(!rcu_is_leaf_node(rnp)), \ + (cpu) = cpumask_next((rnp)->grplo - 1, cpu_possible_mask); \ (cpu) <= rnp->grphi; \ (cpu) = cpumask_next((cpu), cpu_possible_mask)) @@ -335,7 +336,8 @@ static inline void rcu_init_levelspread(int *levelspread, const int *levelcnt) #define rcu_find_next_bit(rnp, cpu, mask) \ ((rnp)->grplo + find_next_bit(&(mask), BITS_PER_LONG, (cpu))) #define for_each_leaf_node_cpu_mask(rnp, cpu, mask) \ - for ((cpu) = rcu_find_next_bit((rnp), 0, (mask)); \ + for (WARN_ON_ONCE(!rcu_is_leaf_node(rnp)), \ + (cpu) = rcu_find_next_bit((rnp), 0, (mask)); \ (cpu) <= rnp->grphi; \ (cpu) = rcu_find_next_bit((rnp), (cpu) + 1 - (rnp->grplo), (mask))) -- cgit From 58c53360b36d2077cbb843e7ad2bf75f0498271c Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Thu, 5 Dec 2019 11:29:01 -0800 Subject: rcutorture: Allow boottime stall warnings to be suppressed In normal production, an RCU CPU stall warning at boottime is often just as bad as at any other time. In fact, given the desire for fast boot, any sort of long-term stall at boot is a bad idea. However, heavy rcutorture testing on large hyperthreaded systems can generate boottime RCU CPU stalls as a matter of course. This commit therefore provides a kernel boot parameter that suppresses reporting of boottime RCU CPU stall warnings and similarly of rcutorture writer stalls. Signed-off-by: Paul E. McKenney --- kernel/rcu/rcu.h | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) (limited to 'kernel/rcu/rcu.h') diff --git a/kernel/rcu/rcu.h b/kernel/rcu/rcu.h index 05f936ed167a..1779cbf33cd1 100644 --- a/kernel/rcu/rcu.h +++ b/kernel/rcu/rcu.h @@ -198,6 +198,13 @@ static inline void debug_rcu_head_unqueue(struct rcu_head *head) } #endif /* #else !CONFIG_DEBUG_OBJECTS_RCU_HEAD */ +extern int rcu_cpu_stall_suppress_at_boot; + +static inline bool rcu_stall_is_suppressed_at_boot(void) +{ + return rcu_cpu_stall_suppress_at_boot && !rcu_inkernel_boot_has_ended(); +} + #ifdef CONFIG_RCU_STALL_COMMON extern int rcu_cpu_stall_ftrace_dump; @@ -205,6 +212,11 @@ extern int rcu_cpu_stall_suppress; extern int rcu_cpu_stall_timeout; int rcu_jiffies_till_stall_check(void); +static inline bool rcu_stall_is_suppressed(void) +{ + return rcu_stall_is_suppressed_at_boot() || rcu_cpu_stall_suppress; +} + #define rcu_ftrace_dump_stall_suppress() \ do { \ if (!rcu_cpu_stall_suppress) \ @@ -218,6 +230,11 @@ do { \ } while (0) #else /* #endif #ifdef CONFIG_RCU_STALL_COMMON */ + +static inline bool rcu_stall_is_suppressed(void) +{ + return rcu_stall_is_suppressed_at_boot(); +} #define rcu_ftrace_dump_stall_suppress() #define rcu_ftrace_dump_stall_unsuppress() #endif /* #ifdef CONFIG_RCU_STALL_COMMON */ -- cgit