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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: Matthew Rosato <mjrosato@linux.ibm.com>
Reviewed-by: Pierre Morel <pmorel@linux.ibm.com>
Signed-off-by: Niklas Schnelle <schnelle@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
This commit is contained in:
Niklas Schnelle 2021-02-12 10:16:46 +01:00 committed by Heiko Carstens
parent a50297cf82
commit 0350276168
1 changed files with 7 additions and 7 deletions
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14
arch/s390/pci/pci_bus.c
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@ -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);