panic: Fix a possible deadlock in panic()
panic_lock is meant to ensure that panic processing takes
place only on one cpu; if any of the other cpus encounter
a panic, they will spin waiting to be shut down.
However, this causes a regression in this scenario:
1. Cpu 0 encounters a panic and acquires the panic_lock
and proceeds with the panic processing.
2. There is an interrupt on cpu 0 that also encounters
an error condition and invokes panic.
3. This second invocation fails to acquire the panic_lock
and enters the infinite while loop in panic_smp_self_stop.
Thus all panic processing is stopped, and the cpu is stuck
for eternity in the while(1) inside panic_smp_self_stop.
To address this, disable local interrupts with
local_irq_disable before acquiring the panic_lock. This will
prevent interrupt handlers from executing during the panic
processing, thus avoiding this particular problem.
Signed-off-by: Vikram Mulukutla <markivx@codeaurora.org>
(cherry picked from commit dd58afef43357f265e803c317bbaa91f8c440663)
Change-Id: I5f7ebcf2a028df265a57922b6c959e686a82026a
Signed-off-by: Swetha Basineni <sbasin@codeaurora.org>
diff --git a/kernel/panic.c b/kernel/panic.c
index 84595f3..c00b0a8 100644
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -92,6 +92,14 @@
local_irq_disable();
/*
+ * Disable local interrupts. This will prevent panic_smp_self_stop
+ * from deadlocking the first cpu that invokes the panic, since
+ * there is nothing to prevent an interrupt handler (that runs
+ * after the panic_lock is acquired) from invoking panic again.
+ */
+ local_irq_disable();
+
+ /*
* It's possible to come here directly from a panic-assertion and
* not have preempt disabled. Some functions called from here want
* preempt to be disabled. No point enabling it later though...