Commit-ID: 62075e581802ea1842d5d3c490a7e46330bdb9e1
Gitweb: http://git.kernel.org/tip/62075e581802ea1842d5d3c490a7e46330bdb9e1
Author: Matt Fleming <matt@xxxxxxxxxxxxxxxxxxx>
AuthorDate: Fri, 6 May 2016 22:39:27 +0100
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Sat, 7 May 2016 07:06:13 +0200
efi/capsule: Make efi_capsule_pending() lockless
Taking a mutex in the reboot path is bogus because we cannot sleep
with interrupts disabled, such as when rebooting due to panic(),
BUG: sleeping function called from invalid context at kernel/locking/mutex.c:97
in_atomic(): 0, irqs_disabled(): 1, pid: 7, name: rcu_sched
Call Trace:
dump_stack+0x63/0x89
___might_sleep+0xd8/0x120
__might_sleep+0x49/0x80
mutex_lock+0x20/0x50
efi_capsule_pending+0x1d/0x60
native_machine_emergency_restart+0x59/0x280
machine_emergency_restart+0x19/0x20
emergency_restart+0x18/0x20
panic+0x1ba/0x217
In this case all other CPUs will have been stopped by the time we
execute the platform reboot code, so 'capsule_pending' cannot change
under our feet. We wouldn't care even if it could since we cannot wait
for it complete.
Also, instead of relying on the external 'system_state' variable just
use a reboot notifier, so we can set 'stop_capsules' while holding
'capsule_mutex', thereby avoiding a race where system_state is updated
while we're in the middle of efi_capsule_update_locked() (since CPUs
won't have been stopped at that point).
Signed-off-by: Matt Fleming <matt@xxxxxxxxxxxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
Cc: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Brian Gerst <brgerst@xxxxxxxxx>
Cc: Bryan O'Donoghue <pure.logic@xxxxxxxxxxxxxxxxx>
Cc: Denys Vlasenko <dvlasenk@xxxxxxxxxx>
Cc: H. Peter Anvin <hpa@xxxxxxxxx>
Cc: Kweh Hock Leong <hock.leong.kweh@xxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: joeyli <jlee@xxxxxxxx>
Cc: linux-efi@xxxxxxxxxxxxxxx
Link: http://lkml.kernel.org/r/1462570771-13324-2-git-send-email-matt@xxxxxxxxxxxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
drivers/firmware/efi/capsule.c | 35 +++++++++++++++++++++++++----------
1 file changed, 25 insertions(+), 10 deletions(-)
diff --git a/drivers/firmware/efi/capsule.c b/drivers/firmware/efi/capsule.c
index 0de5594..e530540 100644
--- a/drivers/firmware/efi/capsule.c
+++ b/drivers/firmware/efi/capsule.c
@@ -22,11 +22,12 @@ typedef struct {
} efi_capsule_block_desc_t;
static bool capsule_pending;
+static bool stop_capsules;
static int efi_reset_type = -1;
/*
* capsule_mutex serialises access to both capsule_pending and
- * efi_reset_type.
+ * efi_reset_type and stop_capsules.
*/
static DEFINE_MUTEX(capsule_mutex);
@@ -50,18 +51,13 @@ static DEFINE_MUTEX(capsule_mutex);
*/
bool efi_capsule_pending(int *reset_type)
{
- bool rv = false;
-
- mutex_lock(&capsule_mutex);
if (!capsule_pending)
- goto out;
+ return false;
if (reset_type)
*reset_type = efi_reset_type;
- rv = true;
-out:
- mutex_unlock(&capsule_mutex);
- return rv;
+
+ return true;
}
/*
@@ -176,7 +172,7 @@ efi_capsule_update_locked(efi_capsule_header_t *capsule,
* whether to force an EFI reboot), and we're racing against
* that call. Abort in that case.
*/
- if (unlikely(system_state == SYSTEM_RESTART)) {
+ if (unlikely(stop_capsules)) {
pr_warn("Capsule update raced with reboot, aborting.\n");
return -EINVAL;
}
@@ -298,3 +294,22 @@ out:
return rv;
}
EXPORT_SYMBOL_GPL(efi_capsule_update);
+
+static int capsule_reboot_notify(struct notifier_block *nb, unsigned long event, void *cmd)
+{
+ mutex_lock(&capsule_mutex);
+ stop_capsules = true;
+ mutex_unlock(&capsule_mutex);
+
+ return NOTIFY_DONE;
+}
+
+static struct notifier_block capsule_reboot_nb = {
+ .notifier_call = capsule_reboot_notify,
+};
+
+static int __init capsule_reboot_register(void)
+{
+ return register_reboot_notifier(&capsule_reboot_nb);
+}
+core_initcall(capsule_reboot_register);
--
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