efivars: Disable external interrupt while holding efivars->lock

[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>

1 files changed, 44 insertions, 42 deletions

diff --git a/drivers/firmware/efivars.c b/drivers/firmware/efivars.c
index ef5070d86f88..a64fb7bda365 100644
--- a/drivers/firmware/efivars.c
+++ b/drivers/firmware/efivars.c
@@ -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",
@@ -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",
@@ -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;
@@ -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)
@@ -754,7 +755,7 @@ 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,
@@ -762,7 +763,7 @@ static ssize_t efivarfs_file_write(struct file *file,
                                             data);
 
         if (status != EFI_SUCCESS) {
-                spin_unlock(&efivars->lock);
+                spin_unlock_irq(&efivars->lock);
                 kfree(data);
 
                 return efi_status_to_err(status);
@@ -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);
         }
@@ -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);
@@ -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);
@@ -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:
@@ -984,7 +985,7 @@ 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,
@@ -992,14 +993,14 @@ static int efivarfs_unlink(struct inode *dir, struct dentry *dentry)
 
         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;
 };
 
@@ -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;
@@ -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;
@@ -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;
 }
 
@@ -1208,6 +1209,7 @@ 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)) {
                 /*
@@ -1215,10 +1217,10 @@ static int efi_pstore_write(enum pstore_type_id type,
                  * 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.
@@ -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;
         }
@@ -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,
@@ -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];
@@ -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);
@@ -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?
@@ -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;
         }
 
@@ -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,
@@ -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?
@@ -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 */
@@ -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.... */
@@ -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;
 }
@@ -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)