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CSD lock commits for v6.5 

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.
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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
This commit is contained in:
Linus Torvalds 2023-08-28 13:46:41 -07:00
parent 6ae0c15765 0d3a00b370
commit b324696dce
1 changed files with 11 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

13
kernel/smp.c
View File

@ -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);