mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-08-26 10:49:33 +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>
339 lines
8.2 KiB
C
339 lines
8.2 KiB
C
/*
|
|
* Persistent Storage - platform driver interface parts.
|
|
*
|
|
* Copyright (C) 2007-2008 Google, Inc.
|
|
* Copyright (C) 2010 Intel Corporation <tony.luck@intel.com>
|
|
*
|
|
* 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
|
|
*/
|
|
|
|
#include <linux/atomic.h>
|
|
#include <linux/types.h>
|
|
#include <linux/errno.h>
|
|
#include <linux/init.h>
|
|
#include <linux/kmsg_dump.h>
|
|
#include <linux/console.h>
|
|
#include <linux/module.h>
|
|
#include <linux/pstore.h>
|
|
#include <linux/string.h>
|
|
#include <linux/timer.h>
|
|
#include <linux/slab.h>
|
|
#include <linux/uaccess.h>
|
|
#include <linux/hardirq.h>
|
|
#include <linux/jiffies.h>
|
|
#include <linux/workqueue.h>
|
|
|
|
#include "internal.h"
|
|
|
|
/*
|
|
* We defer making "oops" entries appear in pstore - see
|
|
* whether the system is actually still running well enough
|
|
* to let someone see the entry
|
|
*/
|
|
static int pstore_update_ms = -1;
|
|
module_param_named(update_ms, pstore_update_ms, int, 0600);
|
|
MODULE_PARM_DESC(update_ms, "milliseconds before pstore updates its content "
|
|
"(default is -1, which means runtime updates are disabled; "
|
|
"enabling this option is not safe, it may lead to further "
|
|
"corruption on Oopses)");
|
|
|
|
static int pstore_new_entry;
|
|
|
|
static void pstore_timefunc(unsigned long);
|
|
static DEFINE_TIMER(pstore_timer, pstore_timefunc, 0, 0);
|
|
|
|
static void pstore_dowork(struct work_struct *);
|
|
static DECLARE_WORK(pstore_work, pstore_dowork);
|
|
|
|
/*
|
|
* pstore_lock just protects "psinfo" during
|
|
* calls to pstore_register()
|
|
*/
|
|
static DEFINE_SPINLOCK(pstore_lock);
|
|
struct pstore_info *psinfo;
|
|
|
|
static char *backend;
|
|
|
|
/* How much of the console log to snapshot */
|
|
static unsigned long kmsg_bytes = 10240;
|
|
|
|
void pstore_set_kmsg_bytes(int bytes)
|
|
{
|
|
kmsg_bytes = bytes;
|
|
}
|
|
|
|
/* Tag each group of saved records with a sequence number */
|
|
static int oopscount;
|
|
|
|
static const char *get_reason_str(enum kmsg_dump_reason reason)
|
|
{
|
|
switch (reason) {
|
|
case KMSG_DUMP_PANIC:
|
|
return "Panic";
|
|
case KMSG_DUMP_OOPS:
|
|
return "Oops";
|
|
case KMSG_DUMP_EMERG:
|
|
return "Emergency";
|
|
case KMSG_DUMP_RESTART:
|
|
return "Restart";
|
|
case KMSG_DUMP_HALT:
|
|
return "Halt";
|
|
case KMSG_DUMP_POWEROFF:
|
|
return "Poweroff";
|
|
default:
|
|
return "Unknown";
|
|
}
|
|
}
|
|
|
|
bool pstore_cannot_block_path(enum kmsg_dump_reason reason)
|
|
{
|
|
/*
|
|
* In case of NMI path, pstore shouldn't be blocked
|
|
* regardless of reason.
|
|
*/
|
|
if (in_nmi())
|
|
return true;
|
|
|
|
switch (reason) {
|
|
/* In panic case, other cpus are stopped by smp_send_stop(). */
|
|
case KMSG_DUMP_PANIC:
|
|
/* Emergency restart shouldn't be blocked by spin lock. */
|
|
case KMSG_DUMP_EMERG:
|
|
return true;
|
|
default:
|
|
return false;
|
|
}
|
|
}
|
|
EXPORT_SYMBOL_GPL(pstore_cannot_block_path);
|
|
|
|
/*
|
|
* callback from kmsg_dump. (s2,l2) has the most recently
|
|
* written bytes, older bytes are in (s1,l1). Save as much
|
|
* as we can from the end of the buffer.
|
|
*/
|
|
static void pstore_dump(struct kmsg_dumper *dumper,
|
|
enum kmsg_dump_reason reason)
|
|
{
|
|
unsigned long total = 0;
|
|
const char *why;
|
|
u64 id;
|
|
unsigned int part = 1;
|
|
unsigned long flags = 0;
|
|
int is_locked = 0;
|
|
int ret;
|
|
|
|
why = get_reason_str(reason);
|
|
|
|
if (pstore_cannot_block_path(reason)) {
|
|
is_locked = spin_trylock_irqsave(&psinfo->buf_lock, flags);
|
|
if (!is_locked) {
|
|
pr_err("pstore dump routine blocked in %s path, may corrupt error record\n"
|
|
, in_nmi() ? "NMI" : why);
|
|
}
|
|
} else
|
|
spin_lock_irqsave(&psinfo->buf_lock, flags);
|
|
oopscount++;
|
|
while (total < kmsg_bytes) {
|
|
char *dst;
|
|
unsigned long size;
|
|
int hsize;
|
|
size_t len;
|
|
|
|
dst = psinfo->buf;
|
|
hsize = sprintf(dst, "%s#%d Part%d\n", why, oopscount, part);
|
|
size = psinfo->bufsize - hsize;
|
|
dst += hsize;
|
|
|
|
if (!kmsg_dump_get_buffer(dumper, true, dst, size, &len))
|
|
break;
|
|
|
|
ret = psinfo->write(PSTORE_TYPE_DMESG, reason, &id, part,
|
|
oopscount, hsize + len, psinfo);
|
|
if (ret == 0 && reason == KMSG_DUMP_OOPS && pstore_is_mounted())
|
|
pstore_new_entry = 1;
|
|
|
|
total += hsize + len;
|
|
part++;
|
|
}
|
|
if (pstore_cannot_block_path(reason)) {
|
|
if (is_locked)
|
|
spin_unlock_irqrestore(&psinfo->buf_lock, flags);
|
|
} else
|
|
spin_unlock_irqrestore(&psinfo->buf_lock, flags);
|
|
}
|
|
|
|
static struct kmsg_dumper pstore_dumper = {
|
|
.dump = pstore_dump,
|
|
};
|
|
|
|
#ifdef CONFIG_PSTORE_CONSOLE
|
|
static void pstore_console_write(struct console *con, const char *s, unsigned c)
|
|
{
|
|
const char *e = s + c;
|
|
|
|
while (s < e) {
|
|
unsigned long flags;
|
|
u64 id;
|
|
|
|
if (c > psinfo->bufsize)
|
|
c = psinfo->bufsize;
|
|
|
|
if (oops_in_progress) {
|
|
if (!spin_trylock_irqsave(&psinfo->buf_lock, flags))
|
|
break;
|
|
} else {
|
|
spin_lock_irqsave(&psinfo->buf_lock, flags);
|
|
}
|
|
memcpy(psinfo->buf, s, c);
|
|
psinfo->write(PSTORE_TYPE_CONSOLE, 0, &id, 0, 0, c, psinfo);
|
|
spin_unlock_irqrestore(&psinfo->buf_lock, flags);
|
|
s += c;
|
|
c = e - s;
|
|
}
|
|
}
|
|
|
|
static struct console pstore_console = {
|
|
.name = "pstore",
|
|
.write = pstore_console_write,
|
|
.flags = CON_PRINTBUFFER | CON_ENABLED | CON_ANYTIME,
|
|
.index = -1,
|
|
};
|
|
|
|
static void pstore_register_console(void)
|
|
{
|
|
register_console(&pstore_console);
|
|
}
|
|
#else
|
|
static void pstore_register_console(void) {}
|
|
#endif
|
|
|
|
static int pstore_write_compat(enum pstore_type_id type,
|
|
enum kmsg_dump_reason reason,
|
|
u64 *id, unsigned int part, int count,
|
|
size_t size, struct pstore_info *psi)
|
|
{
|
|
return psi->write_buf(type, reason, id, part, psinfo->buf, size, psi);
|
|
}
|
|
|
|
/*
|
|
* platform specific persistent storage driver registers with
|
|
* us here. If pstore is already mounted, call the platform
|
|
* read function right away to populate the file system. If not
|
|
* then the pstore mount code will call us later to fill out
|
|
* the file system.
|
|
*
|
|
* Register with kmsg_dump to save last part of console log on panic.
|
|
*/
|
|
int pstore_register(struct pstore_info *psi)
|
|
{
|
|
struct module *owner = psi->owner;
|
|
|
|
spin_lock(&pstore_lock);
|
|
if (psinfo) {
|
|
spin_unlock(&pstore_lock);
|
|
return -EBUSY;
|
|
}
|
|
|
|
if (backend && strcmp(backend, psi->name)) {
|
|
spin_unlock(&pstore_lock);
|
|
return -EINVAL;
|
|
}
|
|
|
|
if (!psi->write)
|
|
psi->write = pstore_write_compat;
|
|
psinfo = psi;
|
|
mutex_init(&psinfo->read_mutex);
|
|
spin_unlock(&pstore_lock);
|
|
|
|
if (owner && !try_module_get(owner)) {
|
|
psinfo = NULL;
|
|
return -EINVAL;
|
|
}
|
|
|
|
if (pstore_is_mounted())
|
|
pstore_get_records(0);
|
|
|
|
kmsg_dump_register(&pstore_dumper);
|
|
pstore_register_console();
|
|
pstore_register_ftrace();
|
|
|
|
if (pstore_update_ms >= 0) {
|
|
pstore_timer.expires = jiffies +
|
|
msecs_to_jiffies(pstore_update_ms);
|
|
add_timer(&pstore_timer);
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
EXPORT_SYMBOL_GPL(pstore_register);
|
|
|
|
/*
|
|
* Read all the records from the persistent store. Create
|
|
* files in our filesystem. Don't warn about -EEXIST errors
|
|
* when we are re-scanning the backing store looking to add new
|
|
* error records.
|
|
*/
|
|
void pstore_get_records(int quiet)
|
|
{
|
|
struct pstore_info *psi = psinfo;
|
|
char *buf = NULL;
|
|
ssize_t size;
|
|
u64 id;
|
|
int count;
|
|
enum pstore_type_id type;
|
|
struct timespec time;
|
|
int failed = 0, rc;
|
|
|
|
if (!psi)
|
|
return;
|
|
|
|
mutex_lock(&psi->read_mutex);
|
|
if (psi->open && psi->open(psi))
|
|
goto out;
|
|
|
|
while ((size = psi->read(&id, &type, &count, &time, &buf, psi)) > 0) {
|
|
rc = pstore_mkfile(type, psi->name, id, count, buf,
|
|
(size_t)size, time, psi);
|
|
kfree(buf);
|
|
buf = NULL;
|
|
if (rc && (rc != -EEXIST || !quiet))
|
|
failed++;
|
|
}
|
|
if (psi->close)
|
|
psi->close(psi);
|
|
out:
|
|
mutex_unlock(&psi->read_mutex);
|
|
|
|
if (failed)
|
|
printk(KERN_WARNING "pstore: failed to load %d record(s) from '%s'\n",
|
|
failed, psi->name);
|
|
}
|
|
|
|
static void pstore_dowork(struct work_struct *work)
|
|
{
|
|
pstore_get_records(1);
|
|
}
|
|
|
|
static void pstore_timefunc(unsigned long dummy)
|
|
{
|
|
if (pstore_new_entry) {
|
|
pstore_new_entry = 0;
|
|
schedule_work(&pstore_work);
|
|
}
|
|
|
|
mod_timer(&pstore_timer, jiffies + msecs_to_jiffies(pstore_update_ms));
|
|
}
|
|
|
|
module_param(backend, charp, 0444);
|
|
MODULE_PARM_DESC(backend, "Pstore backend to use");
|