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68412b1718
commit 9f244e9cfd upstream.
[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>
Cc: CAI Qian <caiqian@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
71 lines
2 KiB
C
71 lines
2 KiB
C
/*
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* Persistent Storage - pstore.h
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*
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* Copyright (C) 2010 Intel Corporation <tony.luck@intel.com>
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*
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* This code is the generic layer to export data records from platform
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* level persistent storage via a file system.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*/
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#ifndef _LINUX_PSTORE_H
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#define _LINUX_PSTORE_H
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#include <linux/time.h>
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#include <linux/kmsg_dump.h>
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/* types */
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enum pstore_type_id {
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PSTORE_TYPE_DMESG = 0,
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PSTORE_TYPE_MCE = 1,
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PSTORE_TYPE_UNKNOWN = 255
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};
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struct pstore_info {
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struct module *owner;
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char *name;
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spinlock_t buf_lock; /* serialize access to 'buf' */
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char *buf;
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size_t bufsize;
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struct mutex read_mutex; /* serialize open/read/close */
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int (*open)(struct pstore_info *psi);
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int (*close)(struct pstore_info *psi);
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ssize_t (*read)(u64 *id, enum pstore_type_id *type,
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struct timespec *time, char **buf,
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struct pstore_info *psi);
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int (*write)(enum pstore_type_id type,
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enum kmsg_dump_reason reason, u64 *id,
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unsigned int part, size_t size, struct pstore_info *psi);
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int (*erase)(enum pstore_type_id type, u64 id,
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struct pstore_info *psi);
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void *data;
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};
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#ifdef CONFIG_PSTORE
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extern int pstore_register(struct pstore_info *);
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extern bool pstore_cannot_block_path(enum kmsg_dump_reason reason);
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#else
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static inline int
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pstore_register(struct pstore_info *psi)
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{
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return -ENODEV;
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}
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static inline bool
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pstore_cannot_block_path(enum kmsg_dump_reason reason)
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{
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return false;
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}
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#endif
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#endif /*_LINUX_PSTORE_H*/
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