Commit 03502761 authored by Niklas Schnelle's avatar Niklas Schnelle Committed by Heiko Carstens
Browse files

s390/pci: use mutex not spinlock for zbus list 



In a later change we will first collect all PCI functions from the CLP
List PCI functions call, then register them to/creating the relevant
zbus. Then only after we've created our virtual bus structure will we
scan all zbusses iterating over the zbus list. Since scanning is
relatively slow a spinlock is a bad fit for protecting the
loop over the devices on the zbus. Furthermore doing the probing on the
bus we need to use pci_lock_rescan_remove() as devices are added to
the PCI subsystem and that is a mutex which can't be locked nested
inside a spinlock section. Note that the contention of this lock should
be very low either way as zbusses are only added/removed concurrently on
hotplug events.

Reviewed-by: default avatarMatthew Rosato <mjrosato@linux.ibm.com>
Reviewed-by: default avatarPierre Morel <pmorel@linux.ibm.com>
Signed-off-by: default avatarNiklas Schnelle <schnelle@linux.ibm.com>
Signed-off-by: default avatarHeiko Carstens <hca@linux.ibm.com>
parent a50297cf

arch/s390/pci/pci_bus.c

+7 −7
Original line number Diff line number Diff line
@@ -27,7 +27,7 @@ 
#include "pci_iov.h"



static LIST_HEAD(zbus_list);

static DEFINE_SPINLOCK(zbus_list_lock);

static DEFINE_MUTEX(zbus_list_lock);

static int zpci_nb_devices;



/* zpci_bus_prepare_device - Prepare a zPCI function for scanning
@@ -214,9 +214,9 @@ static void zpci_bus_release(struct kref *kref) 
		pci_unlock_rescan_remove();

	}



	spin_lock(&zbus_list_lock);

	mutex_lock(&zbus_list_lock);

	list_del(&zbus->bus_next);

	spin_unlock(&zbus_list_lock);

	mutex_unlock(&zbus_list_lock);

	kfree(zbus);

}
@@ -229,7 +229,7 @@ static struct zpci_bus *zpci_bus_get(int pchid) 
{

	struct zpci_bus *zbus;



	spin_lock(&zbus_list_lock);

	mutex_lock(&zbus_list_lock);

	list_for_each_entry(zbus, &zbus_list, bus_next) {

		if (pchid == zbus->pchid) {

			kref_get(&zbus->kref);
@@ -238,7 +238,7 @@ static struct zpci_bus *zpci_bus_get(int pchid) 
	}

	zbus = NULL;

out_unlock:

	spin_unlock(&zbus_list_lock);

	mutex_unlock(&zbus_list_lock);

	return zbus;

}
@@ -252,9 +252,9 @@ static struct zpci_bus *zpci_bus_alloc(int pchid) 


	zbus->pchid = pchid;

	INIT_LIST_HEAD(&zbus->bus_next);

	spin_lock(&zbus_list_lock);

	mutex_lock(&zbus_list_lock);

	list_add_tail(&zbus->bus_next, &zbus_list);

	spin_unlock(&zbus_list_lock);

	mutex_unlock(&zbus_list_lock);



	kref_init(&zbus->kref);

	INIT_LIST_HEAD(&zbus->resources);