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authorSeiji Aguchi <seiji.aguchi@hds.com>2013-01-11 22:10:05 +0400
committerTony Luck <tony.luck@intel.com>2013-01-11 22:21:56 +0400
commite59310adf5eebce108f78b6c47bb330aae2e1666 (patch)
tree755e6f7348fd37094a856595f4ab33ffc5635ce2 /drivers/firmware
parent9f244e9cfd70c7c0f82d3c92ce772ab2a92d9f64 (diff)
downloadlinux-e59310adf5eebce108f78b6c47bb330aae2e1666.tar.xz
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/firmware')
-rw-r--r--drivers/firmware/efivars.c11
1 files changed, 10 insertions, 1 deletions
diff --git a/drivers/firmware/efivars.c b/drivers/firmware/efivars.c
index 7b1c37497c9a..ef5070d86f88 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.