mirrors/linux
1
0
Fork 1
mirror of https://github.com/torvalds/linux.git synced 2025-11-04 10:40:15 +02:00
Code Issues Projects Releases Packages Wiki Activity Actions

rcu: Silence lockdep false positive for expedited grace periods

Browse source 
In a CONFIG_PREEMPT=y kernel, synchronize_rcu_expedited()
acquires the ->exp_funnel_mutex in rcu_preempt_state, then invokes
synchronize_sched_expedited, which acquires the ->exp_funnel_mutex in
rcu_sched_state.  There can be no deadlock because rcu_preempt_state
->exp_funnel_mutex acquisition always precedes that of rcu_sched_state.
But lockdep does not know that, so it gives false-positive splats.

This commit therefore associates a separate lock_class_key structure
with the rcu_sched_state structure's ->exp_funnel_mutex, allowing
lockdep to see the lock ordering, avoiding the false positives.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
This commit is contained in:
Paul E. McKenney 2015-07-19 15:13:40 -07:00
parent cdacbe1f91
commit af859beaab
2 changed files with 18 additions and 2 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

10
kernel/rcu/tree.c
View file

@ -71,6 +71,7 @@ MODULE_ALIAS("rcutree");
static struct lock_class_key rcu_node_class[RCU_NUM_LVLS]; static struct lock_class_key rcu_node_class[RCU_NUM_LVLS];
static struct lock_class_key rcu_fqs_class[RCU_NUM_LVLS]; static struct lock_class_key rcu_fqs_class[RCU_NUM_LVLS];
static struct lock_class_key rcu_exp_class[RCU_NUM_LVLS]; static struct lock_class_key rcu_exp_class[RCU_NUM_LVLS];
static struct lock_class_key rcu_exp_sched_class[RCU_NUM_LVLS];
/* /*
* In order to export the rcu_state name to the tracing tools, it * In order to export the rcu_state name to the tracing tools, it
@ -4049,6 +4050,7 @@ static void __init rcu_init_one(struct rcu_state *rsp,
static const char * const buf[] = RCU_NODE_NAME_INIT; static const char * const buf[] = RCU_NODE_NAME_INIT;
static const char * const fqs[] = RCU_FQS_NAME_INIT; static const char * const fqs[] = RCU_FQS_NAME_INIT;
static const char * const exp[] = RCU_EXP_NAME_INIT; static const char * const exp[] = RCU_EXP_NAME_INIT;
static const char * const exp_sched[] = RCU_EXP_SCHED_NAME_INIT;
static u8 fl_mask = 0x1; static u8 fl_mask = 0x1;
int levelcnt[RCU_NUM_LVLS]; /* # nodes in each level. */ int levelcnt[RCU_NUM_LVLS]; /* # nodes in each level. */
@ -4108,7 +4110,13 @@ static void __init rcu_init_one(struct rcu_state *rsp,
INIT_LIST_HEAD(&rnp->blkd_tasks); INIT_LIST_HEAD(&rnp->blkd_tasks);
rcu_init_one_nocb(rnp); rcu_init_one_nocb(rnp);
mutex_init(&rnp->exp_funnel_mutex); mutex_init(&rnp->exp_funnel_mutex);
lockdep_set_class_and_name(&rnp->exp_funnel_mutex, if (rsp == &rcu_sched_state)
lockdep_set_class_and_name(
&rnp->exp_funnel_mutex,
&rcu_exp_sched_class[i], exp_sched[i]);
else
lockdep_set_class_and_name(
&rnp->exp_funnel_mutex,
&rcu_exp_class[i], exp[i]); &rcu_exp_class[i], exp[i]);
} }
} }

8
kernel/rcu/tree.h
View file

@ -70,6 +70,8 @@
# define RCU_NODE_NAME_INIT { "rcu_node_0" } # define RCU_NODE_NAME_INIT { "rcu_node_0" }
# define RCU_FQS_NAME_INIT { "rcu_node_fqs_0" } # define RCU_FQS_NAME_INIT { "rcu_node_fqs_0" }
# define RCU_EXP_NAME_INIT { "rcu_node_exp_0" } # define RCU_EXP_NAME_INIT { "rcu_node_exp_0" }
# define RCU_EXP_SCHED_NAME_INIT \
{ "rcu_node_exp_sched_0" }
#elif NR_CPUS <= RCU_FANOUT_2 #elif NR_CPUS <= RCU_FANOUT_2
# define RCU_NUM_LVLS 2 # define RCU_NUM_LVLS 2
# define NUM_RCU_LVL_0 1 # define NUM_RCU_LVL_0 1
@ -79,6 +81,8 @@
# define RCU_NODE_NAME_INIT { "rcu_node_0", "rcu_node_1" } # define RCU_NODE_NAME_INIT { "rcu_node_0", "rcu_node_1" }
# define RCU_FQS_NAME_INIT { "rcu_node_fqs_0", "rcu_node_fqs_1" } # define RCU_FQS_NAME_INIT { "rcu_node_fqs_0", "rcu_node_fqs_1" }
# define RCU_EXP_NAME_INIT { "rcu_node_exp_0", "rcu_node_exp_1" } # define RCU_EXP_NAME_INIT { "rcu_node_exp_0", "rcu_node_exp_1" }
# define RCU_EXP_SCHED_NAME_INIT \
{ "rcu_node_exp_sched_0", "rcu_node_exp_sched_1" }
#elif NR_CPUS <= RCU_FANOUT_3 #elif NR_CPUS <= RCU_FANOUT_3
# define RCU_NUM_LVLS 3 # define RCU_NUM_LVLS 3
# define NUM_RCU_LVL_0 1 # define NUM_RCU_LVL_0 1
@ -89,6 +93,8 @@
# define RCU_NODE_NAME_INIT { "rcu_node_0", "rcu_node_1", "rcu_node_2" } # define RCU_NODE_NAME_INIT { "rcu_node_0", "rcu_node_1", "rcu_node_2" }
# define RCU_FQS_NAME_INIT { "rcu_node_fqs_0", "rcu_node_fqs_1", "rcu_node_fqs_2" } # define RCU_FQS_NAME_INIT { "rcu_node_fqs_0", "rcu_node_fqs_1", "rcu_node_fqs_2" }
# define RCU_EXP_NAME_INIT { "rcu_node_exp_0", "rcu_node_exp_1", "rcu_node_exp_2" } # define RCU_EXP_NAME_INIT { "rcu_node_exp_0", "rcu_node_exp_1", "rcu_node_exp_2" }
# define RCU_EXP_SCHED_NAME_INIT \
{ "rcu_node_exp_sched_0", "rcu_node_exp_sched_1", "rcu_node_exp_sched_2" }
#elif NR_CPUS <= RCU_FANOUT_4 #elif NR_CPUS <= RCU_FANOUT_4
# define RCU_NUM_LVLS 4 # define RCU_NUM_LVLS 4
# define NUM_RCU_LVL_0 1 # define NUM_RCU_LVL_0 1
@ -100,6 +106,8 @@
# define RCU_NODE_NAME_INIT { "rcu_node_0", "rcu_node_1", "rcu_node_2", "rcu_node_3" } # define RCU_NODE_NAME_INIT { "rcu_node_0", "rcu_node_1", "rcu_node_2", "rcu_node_3" }
# define RCU_FQS_NAME_INIT { "rcu_node_fqs_0", "rcu_node_fqs_1", "rcu_node_fqs_2", "rcu_node_fqs_3" } # define RCU_FQS_NAME_INIT { "rcu_node_fqs_0", "rcu_node_fqs_1", "rcu_node_fqs_2", "rcu_node_fqs_3" }
# define RCU_EXP_NAME_INIT { "rcu_node_exp_0", "rcu_node_exp_1", "rcu_node_exp_2", "rcu_node_exp_3" } # define RCU_EXP_NAME_INIT { "rcu_node_exp_0", "rcu_node_exp_1", "rcu_node_exp_2", "rcu_node_exp_3" }
# define RCU_EXP_SCHED_NAME_INIT \
{ "rcu_node_exp_sched_0", "rcu_node_exp_sched_1", "rcu_node_exp_sched_2", "rcu_node_exp_sched_3" }
#else #else
# error "CONFIG_RCU_FANOUT insufficient for NR_CPUS" # error "CONFIG_RCU_FANOUT insufficient for NR_CPUS"
#endif /* #if (NR_CPUS) <= RCU_FANOUT_1 */ #endif /* #if (NR_CPUS) <= RCU_FANOUT_1 */