Revision 38860b2c8bb1b92f61396eb06a63adff916fc31d authored by John David Anglin on 08 November 2021, 21:48:16 UTC, committed by Helge Deller on 13 November 2021, 21:10:56 UTC
For years, there have been random segmentation faults in userspace on SMP PA-RISC machines. It occurred to me that this might be a problem in set_pte_at(). MIPS and some other architectures do cache flushes when installing PTEs with the present bit set. Here I have adapted the code in update_mmu_cache() to flush the kernel mapping when the kernel flush is deferred, or when the kernel mapping may alias with the user mapping. This simplifies calls to update_mmu_cache(). I also changed the barrier in set_pte() from a compiler barrier to a full memory barrier. I know this change is not sufficient to fix the problem. It might not be needed. I have had a few days of operation with 5.14.16 to 5.15.1 and haven't seen any random segmentation faults on rp3440 or c8000 so far. Signed-off-by: John David Anglin <dave.anglin@bell.net> Signed-off-by: Helge Deller <deller@gmx.de> Cc: stable@kernel.org # 5.12+
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ac97_bus.c
// SPDX-License-Identifier: GPL-2.0-or-later
/*
* Linux driver model AC97 bus interface
*
* Author: Nicolas Pitre
* Created: Jan 14, 2005
* Copyright: (C) MontaVista Software Inc.
*/
#include <linux/module.h>
#include <linux/init.h>
#include <linux/device.h>
#include <linux/string.h>
#include <sound/ac97_codec.h>
/*
* snd_ac97_check_id() - Reads and checks the vendor ID of the device
* @ac97: The AC97 device to check
* @id: The ID to compare to
* @id_mask: Mask that is applied to the device ID before comparing to @id
*
* If @id is 0 this function returns true if the read device vendor ID is
* a valid ID. If @id is non 0 this functions returns true if @id
* matches the read vendor ID. Otherwise the function returns false.
*/
static bool snd_ac97_check_id(struct snd_ac97 *ac97, unsigned int id,
unsigned int id_mask)
{
ac97->id = ac97->bus->ops->read(ac97, AC97_VENDOR_ID1) << 16;
ac97->id |= ac97->bus->ops->read(ac97, AC97_VENDOR_ID2);
if (ac97->id == 0x0 || ac97->id == 0xffffffff)
return false;
if (id != 0 && id != (ac97->id & id_mask))
return false;
return true;
}
/**
* snd_ac97_reset() - Reset AC'97 device
* @ac97: The AC'97 device to reset
* @try_warm: Try a warm reset first
* @id: Expected device vendor ID
* @id_mask: Mask that is applied to the device ID before comparing to @id
*
* This function resets the AC'97 device. If @try_warm is true the function
* first performs a warm reset. If the warm reset is successful the function
* returns 1. Otherwise or if @try_warm is false the function issues cold reset
* followed by a warm reset. If this is successful the function returns 0,
* otherwise a negative error code. If @id is 0 any valid device ID will be
* accepted, otherwise only the ID that matches @id and @id_mask is accepted.
*/
int snd_ac97_reset(struct snd_ac97 *ac97, bool try_warm, unsigned int id,
unsigned int id_mask)
{
const struct snd_ac97_bus_ops *ops = ac97->bus->ops;
if (try_warm && ops->warm_reset) {
ops->warm_reset(ac97);
if (snd_ac97_check_id(ac97, id, id_mask))
return 1;
}
if (ops->reset)
ops->reset(ac97);
if (ops->warm_reset)
ops->warm_reset(ac97);
if (snd_ac97_check_id(ac97, id, id_mask))
return 0;
return -ENODEV;
}
EXPORT_SYMBOL_GPL(snd_ac97_reset);
/*
* Let drivers decide whether they want to support given codec from their
* probe method. Drivers have direct access to the struct snd_ac97
* structure and may decide based on the id field amongst other things.
*/
static int ac97_bus_match(struct device *dev, struct device_driver *drv)
{
return 1;
}
struct bus_type ac97_bus_type = {
.name = "ac97",
.match = ac97_bus_match,
};
static int __init ac97_bus_init(void)
{
return bus_register(&ac97_bus_type);
}
subsys_initcall(ac97_bus_init);
static void __exit ac97_bus_exit(void)
{
bus_unregister(&ac97_bus_type);
}
module_exit(ac97_bus_exit);
EXPORT_SYMBOL(ac97_bus_type);
MODULE_LICENSE("GPL");
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