[PATCH 16/33] PCI: Flush PCI probe workqueue on cpuset isolated partition change

Frederic Weisbecker
2025-10-13T20:34:08Z

The HK_TYPE_DOMAIN housekeeping cpumask is now modifyable at runtime. In
order to synchronize against PCI probe works and make sure that no
asynchronous probing is still pending or executing on a newly made
isolated CPU, the housekeeping susbsystem must flush the PCI probe
works.

However the PCI probe works can't be flushed easily since they are
queued to the main per-CPU workqueue pool.

Solve this with creating a PCI probe specific pool and provide and use
the appropriate flushing API.

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
---
drivers/pci/pci-driver.c | 17 ++++++++++++++++-
include/linux/pci.h | 3 +++
kernel/sched/isolation.c | 2 ++
3 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c
index 7b74d22b20f7..ac86aaec8bcf 100644
--- a/drivers/pci/pci-driver.c
+++ b/drivers/pci/pci-driver.c
@@ -337,6 +337,8 @@ static int local_pci_probe(struct drv_dev_and_id *ddi)
return 0;
}

+static struct workqueue_struct *pci_probe_wq;
+
struct pci_probe_arg {
struct drv_dev_and_id *ddi;
struct work_struct work;
@@ -407,7 +409,11 @@ static int pci_call_probe(struct pci_driver *drv, struct pci_dev *dev,
cpu = cpumask_any_and(cpumask_of_node(node),
wq_domain_mask);
if (cpu < nr_cpu_ids) {
- schedule_work_on(cpu, &arg.work);
+ struct workqueue_struct *wq = pci_probe_wq;
+
+ if (WARN_ON_ONCE(!wq))
+ wq = system_percpu_wq;
+ queue_work_on(cpu, wq, &arg.work);
rcu_read_unlock();
flush_work(&arg.work);
error = arg.ret;
@@ -425,6 +431,11 @@ static int pci_call_probe(struct pci_driver *drv, struct pci_dev *dev,
return error;
}

+void pci_probe_flush_workqueue(void)
+{
+ flush_workqueue(pci_probe_wq);
+}
+
/**
* __pci_device_probe - check if a driver wants to claim a specific PCI device
* @drv: driver to call to check if it wants the PCI device
@@ -1760,6 +1771,10 @@ static int __init pci_driver_init(void)
{
int ret;

+ pci_probe_wq = alloc_workqueue("sync_wq", WQ_PERCPU, 0);
+ if (!pci_probe_wq)
+ return -ENOMEM;
+
ret = bus_register(&pci_bus_type);
if (ret)
return ret;
diff --git a/include/linux/pci.h b/include/linux/pci.h
index d1fdf81fbe1e..3281c235b895 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -1175,6 +1175,7 @@ struct pci_bus *pci_create_root_bus(struct device *parent, int bus,
struct pci_ops *ops, void *sysdata,
struct list_head *resources);
int pci_host_probe(struct pci_host_bridge *bridge);
+void pci_probe_flush_workqueue(void);
int pci_bus_insert_busn_res(struct pci_bus *b, int bus, int busmax);
int pci_bus_update_busn_res_end(struct pci_bus *b, int busmax);
void pci_bus_release_busn_res(struct pci_bus *b);
@@ -2037,6 +2038,8 @@ static inline int pci_has_flag(int flag) { return 0; }
_PCI_NOP_ALL(read, *)
_PCI_NOP_ALL(write,)

+static inline void pci_probe_flush_workqueue(void) { }
+
static inline struct pci_dev *pci_get_device(unsigned int vendor,
unsigned int device,
struct pci_dev *from)
diff --git a/kernel/sched/isolation.c b/kernel/sched/isolation.c
index 5cd3d98a2663..b1eea5440484 100644
--- a/kernel/sched/isolation.c
+++ b/kernel/sched/isolation.c
@@ -8,6 +8,7 @@
*
*/
#include <linux/sched/isolation.h>
+#include <linux/pci.h>
#include "sched.h"

enum hk_flags {
@@ -144,6 +145,7 @@ int housekeeping_update(struct cpumask *mask, enum hk_type type)

synchronize_rcu();

+ pci_probe_flush_workqueue();
mem_cgroup_flush_workqueue();
vmstat_flush_workqueue();

--
2.51.0