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efivars: Disable external interrupt while holding efivars->lock
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[Problem]
There is a scenario which efi_pstore fails to log messages in a panic case.

 - CPUA holds an efi_var->lock in either efivarfs parts
   or efi_pstore with interrupt enabled.
 - CPUB panics and sends IPI to CPUA in smp_send_stop().
 - CPUA stops with holding the lock.
 - CPUB kicks efi_pstore_write() via kmsg_dump(KSMG_DUMP_PANIC)
   but it returns without logging messages.

[Patch Description]
This patch disables an external interruption while holding efivars->lock
as follows.

In efi_pstore_write() and get_var_data(), spin_lock/spin_unlock is
replaced by spin_lock_irqsave/spin_unlock_irqrestore because they may
be called in an interrupt context.

In other functions, they are replaced by spin_lock_irq/spin_unlock_irq.
because they are all called from a process context.

By applying this patch, we can avoid the problem above with
a following senario.

 - CPUA holds an efi_var->lock with interrupt disabled.
 - CPUB panics and sends IPI to CPUA in smp_send_stop().
 - CPUA receives the IPI after releasing the lock because it is
   disabling interrupt while holding the lock.
 - CPUB waits for one sec until CPUA releases the lock.
 - CPUB kicks efi_pstore_write() via kmsg_dump(KSMG_DUMP_PANIC)
   And it can hold the lock successfully.

Signed-off-by: Seiji Aguchi <seiji.aguchi@hds.com>
Acked-by: Mike Waychison <mikew@google.com>
Acked-by: Matt Fleming <matt.fleming@intel.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
  • Loading branch information
Seiji Aguchi authored and Tony Luck committed Feb 12, 2013
1 parent e59310a commit 81fa4e5
Showing 1 changed file with 44 additions and 42 deletions.
86 changes: 44 additions & 42 deletions drivers/firmware/efivars.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -405,10 +405,11 @@ static efi_status_t
get_var_data(struct efivars *efivars, struct efi_variable *var)
{
efi_status_t status;
unsigned long flags;

spin_lock(&efivars->lock);
spin_lock_irqsave(&efivars->lock, flags);
status = get_var_data_locked(efivars, var);
spin_unlock(&efivars->lock);
spin_unlock_irqrestore(&efivars->lock, flags);

if (status != EFI_SUCCESS) {
printk(KERN_WARNING "efivars: get_variable() failed 0x%lx!\n",
Expand Down Expand Up @@ -537,14 +538,14 @@ efivar_store_raw(struct efivar_entry *entry, const char *buf, size_t count)
return -EINVAL;
}

spin_lock(&efivars->lock);
spin_lock_irq(&efivars->lock);
status = efivars->ops->set_variable(new_var->VariableName,
&new_var->VendorGuid,
new_var->Attributes,
new_var->DataSize,
new_var->Data);

spin_unlock(&efivars->lock);
spin_unlock_irq(&efivars->lock);

if (status != EFI_SUCCESS) {
printk(KERN_WARNING "efivars: set_variable() failed: status=%lx\n",
Expand Down Expand Up @@ -713,7 +714,7 @@ static ssize_t efivarfs_file_write(struct file *file,
* amounts of memory. Pick a default size of 64K if
* QueryVariableInfo() isn't supported by the firmware.
*/
spin_lock(&efivars->lock);
spin_lock_irq(&efivars->lock);

if (!efivars->ops->query_variable_info)
status = EFI_UNSUPPORTED;
Expand All @@ -723,7 +724,7 @@ static ssize_t efivarfs_file_write(struct file *file,
&remaining_size, &max_size);
}

spin_unlock(&efivars->lock);
spin_unlock_irq(&efivars->lock);

if (status != EFI_SUCCESS) {
if (status != EFI_UNSUPPORTED)
Expand Down Expand Up @@ -754,15 +755,15 @@ static ssize_t efivarfs_file_write(struct file *file,
* set_variable call, and removal of the variable from the efivars
* list (in the case of an authenticated delete).
*/
spin_lock(&efivars->lock);
spin_lock_irq(&efivars->lock);

status = efivars->ops->set_variable(var->var.VariableName,
&var->var.VendorGuid,
attributes, datasize,
data);

if (status != EFI_SUCCESS) {
spin_unlock(&efivars->lock);
spin_unlock_irq(&efivars->lock);
kfree(data);

return efi_status_to_err(status);
Expand All @@ -783,20 +784,20 @@ static ssize_t efivarfs_file_write(struct file *file,
NULL);

if (status == EFI_BUFFER_TOO_SMALL) {
spin_unlock(&efivars->lock);
spin_unlock_irq(&efivars->lock);
mutex_lock(&inode->i_mutex);
i_size_write(inode, newdatasize + sizeof(attributes));
mutex_unlock(&inode->i_mutex);

} else if (status == EFI_NOT_FOUND) {
list_del(&var->list);
spin_unlock(&efivars->lock);
spin_unlock_irq(&efivars->lock);
efivar_unregister(var);
drop_nlink(inode);
dput(file->f_dentry);

} else {
spin_unlock(&efivars->lock);
spin_unlock_irq(&efivars->lock);
pr_warn("efivarfs: inconsistent EFI variable implementation? "
"status = %lx\n", status);
}
Expand All @@ -818,11 +819,11 @@ static ssize_t efivarfs_file_read(struct file *file, char __user *userbuf,
void *data;
ssize_t size = 0;

spin_lock(&efivars->lock);
spin_lock_irq(&efivars->lock);
status = efivars->ops->get_variable(var->var.VariableName,
&var->var.VendorGuid,
&attributes, &datasize, NULL);
spin_unlock(&efivars->lock);
spin_unlock_irq(&efivars->lock);

if (status != EFI_BUFFER_TOO_SMALL)
return efi_status_to_err(status);
Expand All @@ -832,12 +833,12 @@ static ssize_t efivarfs_file_read(struct file *file, char __user *userbuf,
if (!data)
return -ENOMEM;

spin_lock(&efivars->lock);
spin_lock_irq(&efivars->lock);
status = efivars->ops->get_variable(var->var.VariableName,
&var->var.VendorGuid,
&attributes, &datasize,
(data + sizeof(attributes)));
spin_unlock(&efivars->lock);
spin_unlock_irq(&efivars->lock);

if (status != EFI_SUCCESS) {
size = efi_status_to_err(status);
Expand Down Expand Up @@ -965,9 +966,9 @@ static int efivarfs_create(struct inode *dir, struct dentry *dentry,
goto out;

kobject_uevent(&var->kobj, KOBJ_ADD);
spin_lock(&efivars->lock);
spin_lock_irq(&efivars->lock);
list_add(&var->list, &efivars->list);
spin_unlock(&efivars->lock);
spin_unlock_irq(&efivars->lock);
d_instantiate(dentry, inode);
dget(dentry);
out:
Expand All @@ -984,22 +985,22 @@ static int efivarfs_unlink(struct inode *dir, struct dentry *dentry)
struct efivars *efivars = var->efivars;
efi_status_t status;

spin_lock(&efivars->lock);
spin_lock_irq(&efivars->lock);

status = efivars->ops->set_variable(var->var.VariableName,
&var->var.VendorGuid,
0, 0, NULL);

if (status == EFI_SUCCESS || status == EFI_NOT_FOUND) {
list_del(&var->list);
spin_unlock(&efivars->lock);
spin_unlock_irq(&efivars->lock);
efivar_unregister(var);
drop_nlink(dir);
dput(dentry);
return 0;
}

spin_unlock(&efivars->lock);
spin_unlock_irq(&efivars->lock);
return -EINVAL;
};

Expand Down Expand Up @@ -1065,13 +1066,13 @@ static int efivarfs_fill_super(struct super_block *sb, void *data, int silent)
/* copied by the above to local storage in the dentry. */
kfree(name);

spin_lock(&efivars->lock);
spin_lock_irq(&efivars->lock);
efivars->ops->get_variable(entry->var.VariableName,
&entry->var.VendorGuid,
&entry->var.Attributes,
&size,
NULL);
spin_unlock(&efivars->lock);
spin_unlock_irq(&efivars->lock);

mutex_lock(&inode->i_mutex);
inode->i_private = entry;
Expand Down Expand Up @@ -1122,7 +1123,7 @@ static int efi_pstore_open(struct pstore_info *psi)
{
struct efivars *efivars = psi->data;

spin_lock(&efivars->lock);
spin_lock_irq(&efivars->lock);
efivars->walk_entry = list_first_entry(&efivars->list,
struct efivar_entry, list);
return 0;
Expand All @@ -1132,7 +1133,7 @@ static int efi_pstore_close(struct pstore_info *psi)
{
struct efivars *efivars = psi->data;

spin_unlock(&efivars->lock);
spin_unlock_irq(&efivars->lock);
return 0;
}

Expand Down Expand Up @@ -1208,17 +1209,18 @@ static int efi_pstore_write(enum pstore_type_id type,
int i, ret = 0;
u64 storage_space, remaining_space, max_variable_size;
efi_status_t status = EFI_NOT_FOUND;
unsigned long flags;

if (pstore_cannot_block_path(reason)) {
/*
* If the lock is taken by another cpu in non-blocking path,
* this driver returns without entering firmware to avoid
* hanging up.
*/
if (!spin_trylock(&efivars->lock))
if (!spin_trylock_irqsave(&efivars->lock, flags))
return -EBUSY;
} else
spin_lock(&efivars->lock);
spin_lock_irqsave(&efivars->lock, flags);

/*
* Check if there is a space enough to log.
Expand All @@ -1230,7 +1232,7 @@ static int efi_pstore_write(enum pstore_type_id type,
&remaining_space,
&max_variable_size);
if (status || remaining_space < size + DUMP_NAME_LEN * 2) {
spin_unlock(&efivars->lock);
spin_unlock_irqrestore(&efivars->lock, flags);
*id = part;
return -ENOSPC;
}
Expand All @@ -1244,7 +1246,7 @@ static int efi_pstore_write(enum pstore_type_id type,
efivars->ops->set_variable(efi_name, &vendor, PSTORE_EFI_ATTRIBUTES,
size, psi->buf);

spin_unlock(&efivars->lock);
spin_unlock_irqrestore(&efivars->lock, flags);

if (size)
ret = efivar_create_sysfs_entry(efivars,
Expand All @@ -1271,7 +1273,7 @@ static int efi_pstore_erase(enum pstore_type_id type, u64 id, int count,
sprintf(name, "dump-type%u-%u-%d-%lu", type, (unsigned int)id, count,
time.tv_sec);

spin_lock(&efivars->lock);
spin_lock_irq(&efivars->lock);

for (i = 0; i < DUMP_NAME_LEN; i++)
efi_name[i] = name[i];
Expand Down Expand Up @@ -1315,7 +1317,7 @@ static int efi_pstore_erase(enum pstore_type_id type, u64 id, int count,
if (found)
list_del(&found->list);

spin_unlock(&efivars->lock);
spin_unlock_irq(&efivars->lock);

if (found)
efivar_unregister(found);
Expand Down Expand Up @@ -1385,7 +1387,7 @@ static ssize_t efivar_create(struct file *filp, struct kobject *kobj,
return -EINVAL;
}

spin_lock(&efivars->lock);
spin_lock_irq(&efivars->lock);

/*
* Does this variable already exist?
Expand All @@ -1403,7 +1405,7 @@ static ssize_t efivar_create(struct file *filp, struct kobject *kobj,
}
}
if (found) {
spin_unlock(&efivars->lock);
spin_unlock_irq(&efivars->lock);
return -EINVAL;
}

Expand All @@ -1417,10 +1419,10 @@ static ssize_t efivar_create(struct file *filp, struct kobject *kobj,
if (status != EFI_SUCCESS) {
printk(KERN_WARNING "efivars: set_variable() failed: status=%lx\n",
status);
spin_unlock(&efivars->lock);
spin_unlock_irq(&efivars->lock);
return -EIO;
}
spin_unlock(&efivars->lock);
spin_unlock_irq(&efivars->lock);

/* Create the entry in sysfs. Locking is not required here */
status = efivar_create_sysfs_entry(efivars,
Expand Down Expand Up @@ -1448,7 +1450,7 @@ static ssize_t efivar_delete(struct file *filp, struct kobject *kobj,
if (!capable(CAP_SYS_ADMIN))
return -EACCES;

spin_lock(&efivars->lock);
spin_lock_irq(&efivars->lock);

/*
* Does this variable already exist?
Expand All @@ -1466,7 +1468,7 @@ static ssize_t efivar_delete(struct file *filp, struct kobject *kobj,
}
}
if (!found) {
spin_unlock(&efivars->lock);
spin_unlock_irq(&efivars->lock);
return -EINVAL;
}
/* force the Attributes/DataSize to 0 to ensure deletion */
Expand All @@ -1482,12 +1484,12 @@ static ssize_t efivar_delete(struct file *filp, struct kobject *kobj,
if (status != EFI_SUCCESS) {
printk(KERN_WARNING "efivars: set_variable() failed: status=%lx\n",
status);
spin_unlock(&efivars->lock);
spin_unlock_irq(&efivars->lock);
return -EIO;
}
list_del(&search_efivar->list);
/* We need to release this lock before unregistering. */
spin_unlock(&efivars->lock);
spin_unlock_irq(&efivars->lock);
efivar_unregister(search_efivar);

/* It's dead Jim.... */
Expand Down Expand Up @@ -1602,9 +1604,9 @@ efivar_create_sysfs_entry(struct efivars *efivars,
kfree(short_name);
short_name = NULL;

spin_lock(&efivars->lock);
spin_lock_irq(&efivars->lock);
list_add(&new_efivar->list, &efivars->list);
spin_unlock(&efivars->lock);
spin_unlock_irq(&efivars->lock);

return 0;
}
Expand Down Expand Up @@ -1673,9 +1675,9 @@ void unregister_efivars(struct efivars *efivars)
struct efivar_entry *entry, *n;

list_for_each_entry_safe(entry, n, &efivars->list, list) {
spin_lock(&efivars->lock);
spin_lock_irq(&efivars->lock);
list_del(&entry->list);
spin_unlock(&efivars->lock);
spin_unlock_irq(&efivars->lock);
efivar_unregister(entry);
}
if (efivars->new_var)
Expand Down

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