mirrors
/
linux-stable
mirror of https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
1
0
Fork 0
Code Issues Releases Wiki Activity

rcu: Make rcu_cpu_starting() rely on interrupts being disabled 

[ Upstream commit 15d44dfa40 ]

Currently, rcu_cpu_starting() is written so that it might be invoked
with interrupts enabled.  However, it is always called when interrupts
are disabled, either by rcu_init(), notify_cpu_starting(), or from a
call point prior to the call to notify_cpu_starting().

But why bother requiring that interrupts be disabled?  The purpose is
to allow the rcu_data structure's ->beenonline flag to be set after all
early processing has completed for the incoming CPU, thus allowing this
flag to be used to determine when workqueues have been set up for the
incoming CPU, while still allowing this flag to be used as a diagnostic
within rcu_core().

This commit therefore makes rcu_cpu_starting() rely on interrupts being
disabled.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Stable-dep-of: 401b0de3ae ("rcu-tasks: Stop rcu_tasks_invoke_cbs() from using never-onlined CPUs")
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Paul E. McKenney 2023-04-27 10:50:47 -07:00 committed by Greg Kroah-Hartman
parent 5d56a8d670
commit d58f0f0ce6
1 changed files with 5 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

11
kernel/rcu/tree.c
View File

@ -4223,15 +4223,16 @@ int rcutree_offline_cpu(unsigned int cpu)
* Note that this function is special in that it is invoked directly
* from the incoming CPU rather than from the cpuhp_step mechanism.
* This is because this function must be invoked at a precise location.
* This incoming CPU must not have enabled interrupts yet.
*/
void rcu_cpu_starting(unsigned int cpu)
{
unsigned long flags;
unsigned long mask;
struct rcu_data *rdp;
struct rcu_node *rnp;
bool newcpu;
lockdep_assert_irqs_disabled();
rdp = per_cpu_ptr(&rcu_data, cpu);
if (rdp->cpu_started)
return;
@ -4239,7 +4240,6 @@ void rcu_cpu_starting(unsigned int cpu)
rnp = rdp->mynode;
mask = rdp->grpmask;
local_irq_save(flags);
arch_spin_lock(&rcu_state.ofl_lock);
rcu_dynticks_eqs_online();
raw_spin_lock(&rcu_state.barrier_lock);
@ -4258,17 +4258,16 @@ void rcu_cpu_starting(unsigned int cpu)
/* An incoming CPU should never be blocking a grace period. */
if (WARN_ON_ONCE(rnp->qsmask & mask)) { /* RCU waiting on incoming CPU? */
/* rcu_report_qs_rnp() *really* wants some flags to restore */
unsigned long flags2;
unsigned long flags;
local_irq_save(flags2);
local_irq_save(flags);
rcu_disable_urgency_upon_qs(rdp);
/* Report QS -after- changing ->qsmaskinitnext! */
rcu_report_qs_rnp(mask, rnp, rnp->gp_seq, flags2);
rcu_report_qs_rnp(mask, rnp, rnp->gp_seq, flags);
} else {
raw_spin_unlock_rcu_node(rnp);
}
arch_spin_unlock(&rcu_state.ofl_lock);
local_irq_restore(flags);
smp_mb(); /* Ensure RCU read-side usage follows above initialization. */
}