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authorLinus Torvalds <torvalds@linux-foundation.org>2023-08-28 13:46:41 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2023-08-28 13:46:41 -0700
commitb324696dce7a5b1be11c16cbba6ac6643dadd364 (patch)
tree49abec46d7fdce18270fe8be544697b809fb7cb0 /kernel
parent6ae0c157658b26e78eb30b50939ce3dfb794d21f (diff)
parent0d3a00b370424f5f1b9fd037bc8a4a3e7cbf0939 (diff)
Merge tag 'csd-lock.2023.07.15a' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu
Pull CSD lock updates from Paul McKenney: "This series reduces the number of stack traces dumped during CSD-lock debugging. This helps to avoid console overrun on systems with large numbers of CPUs" * tag 'csd-lock.2023.07.15a' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu: smp: Reduce NMI traffic from CSD waiters to CSD destination smp: Reduce logging due to dump_stack of CSD waiters
Diffstat (limited to 'kernel')
-rw-r--r--kernel/smp.c13
1 files changed, 11 insertions, 2 deletions
diff --git a/kernel/smp.c b/kernel/smp.c
index 385179dae360..8455a53465af 100644
--- a/kernel/smp.c
+++ b/kernel/smp.c
@@ -46,6 +46,8 @@ static DEFINE_PER_CPU_ALIGNED(struct call_function_data, cfd_data);
static DEFINE_PER_CPU_SHARED_ALIGNED(struct llist_head, call_single_queue);
+static DEFINE_PER_CPU(atomic_t, trigger_backtrace) = ATOMIC_INIT(1);
+
static void __flush_smp_call_function_queue(bool warn_cpu_offline);
int smpcfd_prepare_cpu(unsigned int cpu)
@@ -253,13 +255,15 @@ static bool csd_lock_wait_toolong(struct __call_single_data *csd, u64 ts0, u64 *
*bug_id, !cpu_cur_csd ? "unresponsive" : "handling this request");
}
if (cpu >= 0) {
- dump_cpu_task(cpu);
+ if (atomic_cmpxchg_acquire(&per_cpu(trigger_backtrace, cpu), 1, 0))
+ dump_cpu_task(cpu);
if (!cpu_cur_csd) {
pr_alert("csd: Re-sending CSD lock (#%d) IPI from CPU#%02d to CPU#%02d\n", *bug_id, raw_smp_processor_id(), cpu);
arch_send_call_function_single_ipi(cpu);
}
}
- dump_stack();
+ if (firsttime)
+ dump_stack();
*ts1 = ts2;
return false;
@@ -433,9 +437,14 @@ static void __flush_smp_call_function_queue(bool warn_cpu_offline)
struct llist_node *entry, *prev;
struct llist_head *head;
static bool warned;
+ atomic_t *tbt;
lockdep_assert_irqs_disabled();
+ /* Allow waiters to send backtrace NMI from here onwards */
+ tbt = this_cpu_ptr(&trigger_backtrace);
+ atomic_set_release(tbt, 1);
+
head = this_cpu_ptr(&call_single_queue);
entry = llist_del_all(head);
entry = llist_reverse_order(entry);