Commit df685633 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge tag 'rcu-fixes.v7.1-20260519a' of git://git.kernel.org/pub/scm/linux/kernel/git/rcu/linux 

Pull RCU fixes from Boqun Feng:
 "Fix a regression introduced by commit 61bbcfb5 ("srcu: Push
  srcu_node allocation to GP when non-preemptible").

  SRCU may queue works on CPUs that are "possible" but never have been
  online. In such a case, the work callbacks may not be executed until
  the corresponding CPU gets online, and as the callbacks accumulates,
  workqueue lockups will fire.

  Fix this by avoiding queuing works on CPUs that have never been
  online"

* tag 'rcu-fixes.v7.1-20260519a' of git://git.kernel.org/pub/scm/linux/kernel/git/rcu/linux:
  srcu: Don't queue workqueue handlers to never-online CPUs
parents e312f536 593889c4

kernel/rcu/srcutree.c

+6 −6
Original line number Diff line number Diff line
@@ -897,12 +897,10 @@ static void srcu_schedule_cbs_snp(struct srcu_struct *ssp, struct srcu_node *snp 
{

	int cpu;



	for (cpu = snp->grplo; cpu <= snp->grphi; cpu++) {

		if (!(mask & (1UL << (cpu - snp->grplo))))

			continue;

	for (cpu = snp->grplo; cpu <= snp->grphi; cpu++)

		if ((mask & (1UL << (cpu - snp->grplo))) && rcu_cpu_beenfullyonline(cpu))

			srcu_schedule_cbs_sdp(per_cpu_ptr(ssp->sda, cpu), delay);

}

}



/*

 * Note the end of an SRCU grace period.  Initiates callback invocation
@@ -1322,7 +1320,9 @@ static unsigned long srcu_gp_start_if_needed(struct srcu_struct *ssp, 
	 */

	idx = __srcu_read_lock_nmisafe(ssp);

	ss_state = smp_load_acquire(&ssp->srcu_sup->srcu_size_state);

	if (ss_state < SRCU_SIZE_WAIT_CALL)

	// If !rcu_cpu_beenfullyonline(), interrupts are still disabled,

	// so no migration is possible in either direction from this CPU.

	if (ss_state < SRCU_SIZE_WAIT_CALL || !rcu_cpu_beenfullyonline(raw_smp_processor_id()))

		sdp = per_cpu_ptr(ssp->sda, get_boot_cpu_id());

	else

		sdp = raw_cpu_ptr(ssp->sda);