mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-09-05 10:29:37 +00:00
![Seiji Aguchi](/assets/img/avatar_default.png)
[Issue] When pstore is in panic and emergency-restart paths, it may be blocked in those paths because it simply takes spin_lock. This is an example scenario which pstore may hang up in a panic path: - cpuA grabs psinfo->buf_lock - cpuB panics and calls smp_send_stop - smp_send_stop sends IRQ to cpuA - after 1 second, cpuB gives up on cpuA and sends an NMI instead - cpuA is now in an NMI handler while still holding buf_lock - cpuB is deadlocked This case may happen if a firmware has a bug and cpuA is stuck talking with it more than one second. Also, this is a similar scenario in an emergency-restart path: - cpuA grabs psinfo->buf_lock and stucks in a firmware - cpuB kicks emergency-restart via either sysrq-b or hangcheck timer. And then, cpuB is deadlocked by taking psinfo->buf_lock again. [Solution] This patch avoids the deadlocking issues in both panic and emergency_restart paths by introducing a function, is_non_blocking_path(), to check if a cpu can be blocked in current path. With this patch, pstore is not blocked even if another cpu has taken a spin_lock, in those paths by changing from spin_lock_irqsave to spin_trylock_irqsave. In addition, according to a comment of emergency_restart() in kernel/sys.c, spin_lock shouldn't be taken in an emergency_restart path to avoid deadlock. This patch fits the comment below. <snip> /** * emergency_restart - reboot the system * * Without shutting down any hardware or taking any locks * reboot the system. This is called when we know we are in * trouble so this is our best effort to reboot. This is * safe to call in interrupt context. */ void emergency_restart(void) <snip> Signed-off-by: Seiji Aguchi <seiji.aguchi@hds.com> Acked-by: Don Zickus <dzickus@redhat.com> Signed-off-by: Tony Luck <tony.luck@intel.com>
85 lines
2.4 KiB
C
85 lines
2.4 KiB
C
/*
|
|
* Persistent Storage - pstore.h
|
|
*
|
|
* Copyright (C) 2010 Intel Corporation <tony.luck@intel.com>
|
|
*
|
|
* This code is the generic layer to export data records from platform
|
|
* level persistent storage via a file system.
|
|
*
|
|
* This program is free software; you can redistribute it and/or modify
|
|
* it under the terms of the GNU General Public License version 2 as
|
|
* published by the Free Software Foundation.
|
|
*
|
|
* This program is distributed in the hope that it will be useful,
|
|
* but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
|
* GNU General Public License for more details.
|
|
*
|
|
* You should have received a copy of the GNU General Public License
|
|
* along with this program; if not, write to the Free Software
|
|
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
|
|
*/
|
|
#ifndef _LINUX_PSTORE_H
|
|
#define _LINUX_PSTORE_H
|
|
|
|
#include <linux/time.h>
|
|
#include <linux/kmsg_dump.h>
|
|
#include <linux/mutex.h>
|
|
#include <linux/types.h>
|
|
#include <linux/spinlock.h>
|
|
#include <linux/errno.h>
|
|
|
|
/* types */
|
|
enum pstore_type_id {
|
|
PSTORE_TYPE_DMESG = 0,
|
|
PSTORE_TYPE_MCE = 1,
|
|
PSTORE_TYPE_CONSOLE = 2,
|
|
PSTORE_TYPE_FTRACE = 3,
|
|
PSTORE_TYPE_UNKNOWN = 255
|
|
};
|
|
|
|
struct module;
|
|
|
|
struct pstore_info {
|
|
struct module *owner;
|
|
char *name;
|
|
spinlock_t buf_lock; /* serialize access to 'buf' */
|
|
char *buf;
|
|
size_t bufsize;
|
|
struct mutex read_mutex; /* serialize open/read/close */
|
|
int (*open)(struct pstore_info *psi);
|
|
int (*close)(struct pstore_info *psi);
|
|
ssize_t (*read)(u64 *id, enum pstore_type_id *type,
|
|
int *count, struct timespec *time, char **buf,
|
|
struct pstore_info *psi);
|
|
int (*write)(enum pstore_type_id type,
|
|
enum kmsg_dump_reason reason, u64 *id,
|
|
unsigned int part, int count, size_t size,
|
|
struct pstore_info *psi);
|
|
int (*write_buf)(enum pstore_type_id type,
|
|
enum kmsg_dump_reason reason, u64 *id,
|
|
unsigned int part, const char *buf, size_t size,
|
|
struct pstore_info *psi);
|
|
int (*erase)(enum pstore_type_id type, u64 id,
|
|
int count, struct timespec time,
|
|
struct pstore_info *psi);
|
|
void *data;
|
|
};
|
|
|
|
#ifdef CONFIG_PSTORE
|
|
extern int pstore_register(struct pstore_info *);
|
|
extern bool pstore_cannot_block_path(enum kmsg_dump_reason reason);
|
|
#else
|
|
static inline int
|
|
pstore_register(struct pstore_info *psi)
|
|
{
|
|
return -ENODEV;
|
|
}
|
|
static inline bool
|
|
pstore_cannot_block_path(enum kmsg_dump_reason reason)
|
|
{
|
|
return false;
|
|
}
|
|
#endif
|
|
|
|
#endif /*_LINUX_PSTORE_H*/
|