Commit abd4d558 authored by Don Zickus's avatar Don Zickus Committed by Tony Luck
Browse files

pstore: change mutex locking to spin_locks 



pstore was using mutex locking to protect read/write access to the
backend plug-ins.  This causes problems when pstore is executed in
an NMI context through panic() -> kmsg_dump().

This patch changes the mutex to a spin_lock_irqsave then also checks to
see if we are in an NMI context.  If we are in an NMI and can't get the
lock, just print a message stating that and blow by the locking.

All this is probably a hack around the bigger locking problem but it
solves my current situation of trying to sleep in an NMI context.

Tested by loading the lkdtm module and executing a HARDLOCKUP which
will cause the machine to panic inside the nmi handler.

Signed-off-by: default avatarDon Zickus <dzickus@redhat.com>
Acked-by: default avatarMatthew Garrett <mjg@redhat.com>
Signed-off-by: default avatarTony Luck <tony.luck@intel.com>
parent 6dda9266

drivers/acpi/apei/erst.c

+1 −1
Original line number Diff line number Diff line
@@ -1165,7 +1165,7 @@ static int __init erst_init(void) 
		goto err_release_erange;



	buf = kmalloc(erst_erange.size, GFP_KERNEL);

	mutex_init(&erst_info.buf_mutex);

	spin_lock_init(&erst_info.buf_lock);

	if (buf) {

		erst_info.buf = buf + sizeof(struct cper_pstore_record);

		erst_info.bufsize = erst_erange.size -

drivers/firmware/efivars.c

+1 −1
Original line number Diff line number Diff line
@@ -978,7 +978,7 @@ int register_efivars(struct efivars *efivars, 
	if (efivars->efi_pstore_info.buf) {

		efivars->efi_pstore_info.bufsize = 1024;

		efivars->efi_pstore_info.data = efivars;

		mutex_init(&efivars->efi_pstore_info.buf_mutex);

		spin_lock_init(&efivars->efi_pstore_info.buf_lock);

		pstore_register(&efivars->efi_pstore_info);

	}

fs/pstore/platform.c

+21 −7
Original line number Diff line number Diff line
@@ -28,6 +28,7 @@ 
#include <linux/timer.h>

#include <linux/slab.h>

#include <linux/uaccess.h>

#include <linux/hardirq.h>

#include <linux/workqueue.h>



#include "internal.h"
@@ -88,13 +89,20 @@ static void pstore_dump(struct kmsg_dumper *dumper, 
	u64		id;

	int		hsize;

	unsigned int	part = 1;

	unsigned long	flags = 0;

	int		is_locked = 0;



	if (reason < ARRAY_SIZE(reason_str))

		why = reason_str[reason];

	else

		why = "Unknown";



	mutex_lock(&psinfo->buf_mutex);

	if (in_nmi()) {

		is_locked = spin_trylock(&psinfo->buf_lock);

		if (!is_locked)

			pr_err("pstore dump routine blocked in NMI, may corrupt error record\n");

	} else

		spin_lock_irqsave(&psinfo->buf_lock, flags);

	oopscount++;

	while (total < kmsg_bytes) {

		dst = psinfo->buf;
@@ -123,7 +131,11 @@ static void pstore_dump(struct kmsg_dumper *dumper, 
		total += l1_cpy + l2_cpy;

		part++;

	}

	mutex_unlock(&psinfo->buf_mutex);

	if (in_nmi()) {

		if (is_locked)

			spin_unlock(&psinfo->buf_lock);

	} else

		spin_unlock_irqrestore(&psinfo->buf_lock, flags);

}



static struct kmsg_dumper pstore_dumper = {
@@ -188,11 +200,12 @@ void pstore_get_records(int quiet) 
	enum pstore_type_id	type;

	struct timespec		time;

	int			failed = 0, rc;

	unsigned long		flags;



	if (!psi)

		return;



	mutex_lock(&psinfo->buf_mutex);

	spin_lock_irqsave(&psinfo->buf_lock, flags);

	rc = psi->open(psi);

	if (rc)

		goto out;
@@ -205,7 +218,7 @@ void pstore_get_records(int quiet) 
	}

	psi->close(psi);

out:

	mutex_unlock(&psinfo->buf_mutex);

	spin_unlock_irqrestore(&psinfo->buf_lock, flags);



	if (failed)

		printk(KERN_WARNING "pstore: failed to load %d record(s) from '%s'\n",
@@ -234,6 +247,7 @@ static void pstore_timefunc(unsigned long dummy) 
int pstore_write(enum pstore_type_id type, char *buf, size_t size)

{

	u64		id;

	unsigned long	flags;



	if (!psinfo)

		return -ENODEV;
@@ -241,13 +255,13 @@ int pstore_write(enum pstore_type_id type, char *buf, size_t size) 
	if (size > psinfo->bufsize)

		return -EFBIG;



	mutex_lock(&psinfo->buf_mutex);

	spin_lock_irqsave(&psinfo->buf_lock, flags);

	memcpy(psinfo->buf, buf, size);

	id = psinfo->write(type, 0, size, psinfo);

	if (pstore_is_mounted())

		pstore_mkfile(PSTORE_TYPE_DMESG, psinfo->name, id, psinfo->buf,

			      size, CURRENT_TIME, psinfo);

	mutex_unlock(&psinfo->buf_mutex);

	spin_unlock_irqrestore(&psinfo->buf_lock, flags);



	return 0;

}

include/linux/pstore.h

+1 −1
Original line number Diff line number Diff line
@@ -32,7 +32,7 @@ enum pstore_type_id { 
struct pstore_info {

	struct module	*owner;

	char		*name;

	struct mutex	buf_mutex;	/* serialize access to 'buf' */

	spinlock_t	buf_lock;	/* serialize access to 'buf' */

	char		*buf;

	size_t		bufsize;

	int		(*open)(struct pstore_info *psi);

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