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) {