diff options
| author | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2016-01-03 20:29:57 -0800 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2016-03-31 13:34:50 -0700 |
| commit | 8c7c4829a81c1838f18c12ce5a3a5c29a08bf0a8 (patch) | |
| tree | 0d06174a9f214fb1eb96919d48c490c0fae0db1c /kernel/rcu | |
| parent | fcfd0a237bfcf0c314005007e9d76e55a25e2bad (diff) | |
rcu: Awaken grace-period kthread if too long since FQS
Recent kernels can fail to awaken the grace-period kthread for
quiescent-state forcing. This commit is a crude hack that does
a wakeup if a scheduling-clock interrupt sees that it has been
too long since force-quiescent-state (FQS) processing.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Diffstat (limited to 'kernel/rcu')
| -rw-r--r-- | kernel/rcu/tree.c | 39 | ||||
| -rw-r--r-- | kernel/rcu/tree.h | 2 |
2 files changed, 39 insertions, 2 deletions
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 6116cfad18ff..a739292be605 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -385,9 +385,11 @@ module_param(qlowmark, long, 0444); static ulong jiffies_till_first_fqs = ULONG_MAX; static ulong jiffies_till_next_fqs = ULONG_MAX; +static bool rcu_kick_kthreads; module_param(jiffies_till_first_fqs, ulong, 0644); module_param(jiffies_till_next_fqs, ulong, 0644); +module_param(rcu_kick_kthreads, bool, 0644); /* * How long the grace period must be before we start recruiting @@ -1251,6 +1253,24 @@ static void rcu_dump_cpu_stacks(struct rcu_state *rsp) } } +/* + * If too much time has passed in the current grace period, and if + * so configured, go kick the relevant kthreads. + */ +static void rcu_stall_kick_kthreads(struct rcu_state *rsp) +{ + unsigned long j; + + if (!rcu_kick_kthreads) + return; + j = READ_ONCE(rsp->jiffies_kick_kthreads); + if (time_after(jiffies, j) && rsp->gp_kthread) { + WARN_ONCE(1, "Kicking %s grace-period kthread\n", rsp->name); + wake_up_process(rsp->gp_kthread); + WRITE_ONCE(rsp->jiffies_kick_kthreads, j + HZ); + } +} + static void print_other_cpu_stall(struct rcu_state *rsp, unsigned long gpnum) { int cpu; @@ -1262,6 +1282,11 @@ static void print_other_cpu_stall(struct rcu_state *rsp, unsigned long gpnum) struct rcu_node *rnp = rcu_get_root(rsp); long totqlen = 0; + /* Kick and suppress, if so configured. */ + rcu_stall_kick_kthreads(rsp); + if (rcu_cpu_stall_suppress) + return; + /* Only let one CPU complain about others per time interval. */ raw_spin_lock_irqsave_rcu_node(rnp, flags); @@ -1335,6 +1360,11 @@ static void print_cpu_stall(struct rcu_state *rsp) struct rcu_node *rnp = rcu_get_root(rsp); long totqlen = 0; + /* Kick and suppress, if so configured. */ + rcu_stall_kick_kthreads(rsp); + if (rcu_cpu_stall_suppress) + return; + /* * OK, time to rat on ourselves... * See Documentation/RCU/stallwarn.txt for info on how to debug @@ -1379,8 +1409,10 @@ static void check_cpu_stall(struct rcu_state *rsp, struct rcu_data *rdp) unsigned long js; struct rcu_node *rnp; - if (rcu_cpu_stall_suppress || !rcu_gp_in_progress(rsp)) + if ((rcu_cpu_stall_suppress && !rcu_kick_kthreads) || + !rcu_gp_in_progress(rsp)) return; + rcu_stall_kick_kthreads(rsp); j = jiffies; /* @@ -2119,8 +2151,11 @@ static int __noreturn rcu_gp_kthread(void *arg) } ret = 0; for (;;) { - if (!ret) + if (!ret) { rsp->jiffies_force_qs = jiffies + j; + WRITE_ONCE(rsp->jiffies_kick_kthreads, + jiffies + 3 * j); + } trace_rcu_grace_period(rsp->name, READ_ONCE(rsp->gpnum), TPS("fqswait")); diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h index df668c0f9e64..34d3973f7223 100644 --- a/kernel/rcu/tree.h +++ b/kernel/rcu/tree.h @@ -513,6 +513,8 @@ struct rcu_state { unsigned long jiffies_force_qs; /* Time at which to invoke */ /* force_quiescent_state(). */ + unsigned long jiffies_kick_kthreads; /* Time at which to kick */ + /* kthreads, if configured. */ unsigned long n_force_qs; /* Number of calls to */ /* force_quiescent_state(). */ unsigned long n_force_qs_lh; /* ~Number of calls leaving */ |