diff options
| author | Seiji Aguchi <seiji.aguchi@hds.com> | 2013-01-11 18:10:05 +0000 |
|---|---|---|
| committer | Tony Luck <tony.luck@intel.com> | 2013-01-11 10:21:56 -0800 |
| commit | e59310adf5eebce108f78b6c47bb330aae2e1666 (patch) | |
| tree | 755e6f7348fd37094a856595f4ab33ffc5635ce2 /drivers | |
| parent | 9f244e9cfd70c7c0f82d3c92ce772ab2a92d9f64 (diff) | |
efi_pstore: Avoid deadlock in non-blocking paths
[Issue]
There is a scenario which efi_pstore may hang up:
- cpuA grabs efivars->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 efivars->lock
- cpuB is deadlocked
This case may happen if a firmware has a bug and
cpuA is stuck talking with it.
[Solution]
This patch changes a spin_lock to a spin_trylock in non-blocking paths.
and if the spin_lock has already taken by another cpu,
it returns without accessing to a firmware to avoid the deadlock.
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>
Diffstat (limited to 'drivers')
| -rw-r--r-- | drivers/firmware/efivars.c | 11 |
1 files changed, 10 insertions, 1 deletions
diff --git a/drivers/firmware/efivars.c b/drivers/firmware/efivars.c index 7b1c37497c9..ef5070d86f8 100644 --- a/drivers/firmware/efivars.c +++ b/drivers/firmware/efivars.c @@ -1209,7 +1209,16 @@ static int efi_pstore_write(enum pstore_type_id type, u64 storage_space, remaining_space, max_variable_size; efi_status_t status = EFI_NOT_FOUND; - spin_lock(&efivars->lock); + 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)) + return -EBUSY; + } else + spin_lock(&efivars->lock); /* * Check if there is a space enough to log. |