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authorMatt Fleming <matt@codeblueprint.co.uk>2016-05-06 22:39:27 +0100
committerIngo Molnar <mingo@kernel.org>2016-05-07 07:06:13 +0200
commit62075e581802ea1842d5d3c490a7e46330bdb9e1 (patch)
treed391a38dd26f992e6b136f8497e077620e2aba7a /drivers/firmware
parent35dc9ec1076b79c31bf7ed538af008b7f23bb14d (diff)
downloadop-kernel-dev-62075e581802ea1842d5d3c490a7e46330bdb9e1.zip
op-kernel-dev-62075e581802ea1842d5d3c490a7e46330bdb9e1.tar.gz
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@codeblueprint.co.uk> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: Bryan O'Donoghue <pure.logic@nexus-software.ie> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Kweh Hock Leong <hock.leong.kweh@intel.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: joeyli <jlee@suse.com> Cc: linux-efi@vger.kernel.org Link: http://lkml.kernel.org/r/1462570771-13324-2-git-send-email-matt@codeblueprint.co.uk Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'drivers/firmware')
-rw-r--r--drivers/firmware/efi/capsule.c35
1 files 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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