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

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Pull RCU fixes from Boqun Feng:
 "Fix a regression introduced by commit 61bbcfb505 ("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
This commit is contained in:
Linus Torvalds
2026-05-20 10:15:30 -05:00
parent e312f536f6 593889c401
commit df685633c3
1 changed files with 6 additions and 6 deletions
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12
kernel/rcu/srcutree.c
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@@ -897,11 +897,9 @@ 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;
srcu_schedule_cbs_sdp(per_cpu_ptr(ssp->sda, cpu), delay);
}
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);
}
/*
@@ -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);