The following commit has been merged into the smp/core branch of tip:
Commit-ID: 22b612e2d53f6e13ce7b55ed565a104512f0eb00
Gitweb: https://git.kernel.org/tip/22b612e2d53f6e13ce7b55ed565a104512f0eb00
Author: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
AuthorDate: Fri, 12 May 2023 23:07:21 +02:00
Committer: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CommitterDate: Mon, 15 May 2023 13:44:54 +02:00
cpu/hotplug: Rework sparse_irq locking in bringup_cpu()
There is no harm to hold sparse_irq lock until the upcoming CPU completes
in cpuhp_online_idle(). This allows to remove cpu_online() synchronization
from architecture code.
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Tested-by: Michael Kelley <mikelley@xxxxxxxxxxxxx>
Tested-by: Oleksandr Natalenko <oleksandr@xxxxxxxxxxxxxx>
Tested-by: Helge Deller <deller@xxxxxx> # parisc
Tested-by: Guilherme G. Piccoli <gpiccoli@xxxxxxxxxx> # Steam Deck
Link: https://lore.kernel.org/r/20230512205256.263722880@xxxxxxxxxxxxx
---
kernel/cpu.c | 34 ++++++++++++++++++++++++----------
1 file changed, 24 insertions(+), 10 deletions(-)
diff --git a/kernel/cpu.c b/kernel/cpu.c
index c0d859c..df8f137 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -558,7 +558,7 @@ static int cpuhp_kick_ap(int cpu, struct cpuhp_cpu_state *st,
return ret;
}
-static int bringup_wait_for_ap(unsigned int cpu)
+static int bringup_wait_for_ap_online(unsigned int cpu)
{
struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
@@ -579,15 +579,12 @@ static int bringup_wait_for_ap(unsigned int cpu)
*/
if (!cpu_smt_allowed(cpu))
return -ECANCELED;
-
- if (st->target <= CPUHP_AP_ONLINE_IDLE)
- return 0;
-
- return cpuhp_kick_ap(cpu, st, st->target);
+ return 0;
}
static int bringup_cpu(unsigned int cpu)
{
+ struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
struct task_struct *idle = idle_thread_get(cpu);
int ret;
@@ -600,16 +597,33 @@ static int bringup_cpu(unsigned int cpu)
/*
* Some architectures have to walk the irq descriptors to
* setup the vector space for the cpu which comes online.
- * Prevent irq alloc/free across the bringup.
+ *
+ * Prevent irq alloc/free across the bringup by acquiring the
+ * sparse irq lock. Hold it until the upcoming CPU completes the
+ * startup in cpuhp_online_idle() which allows to avoid
+ * intermediate synchronization points in the architecture code.
*/
irq_lock_sparse();
/* Arch-specific enabling code. */
ret = __cpu_up(cpu, idle);
- irq_unlock_sparse();
if (ret)
- return ret;
- return bringup_wait_for_ap(cpu);
+ goto out_unlock;
+
+ ret = bringup_wait_for_ap_online(cpu);
+ if (ret)
+ goto out_unlock;
+
+ irq_unlock_sparse();
+
+ if (st->target <= CPUHP_AP_ONLINE_IDLE)
+ return 0;
+
+ return cpuhp_kick_ap(cpu, st, st->target);
+
+out_unlock:
+ irq_unlock_sparse();
+ return ret;
}
static int finish_cpu(unsigned int cpu)
|