riscv: Fix sleeping in invalid context in die()

die() can be called in exception handler, and therefore cannot sleep.
However, die() takes spinlock_t which can sleep with PREEMPT_RT enabled.
That causes the following warning:

BUG: sleeping function called from invalid context at kernel/locking/spinlock_rt.c:48
in_atomic(): 1, irqs_disabled(): 1, non_block: 0, pid: 285, name: mutex
preempt_count: 110001, expected: 0
RCU nest depth: 0, expected: 0
CPU: 0 UID: 0 PID: 285 Comm: mutex Not tainted 6.12.0-rc7-00022-ge19049cf7d56-dirty #234
Hardware name: riscv-virtio,qemu (DT)
Call Trace:
    dump_backtrace+0x1c/0x24
    show_stack+0x2c/0x38
    dump_stack_lvl+0x5a/0x72
    dump_stack+0x14/0x1c
    __might_resched+0x130/0x13a
    rt_spin_lock+0x2a/0x5c
    die+0x24/0x112
    do_trap_insn_illegal+0xa0/0xea
    _new_vmalloc_restore_context_a0+0xcc/0xd8
Oops - illegal instruction [#1]

Switch to use raw_spinlock_t, which does not sleep even with PREEMPT_RT
enabled.

Fixes: 76d2a04 ("RISC-V: Init and Halt Code")
Signed-off-by: Nam Cao <[email protected]>
Cc: [email protected]
Reviewed-by: Sebastian Andrzej Siewior <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Palmer Dabbelt <[email protected]>

arch/riscv/kernel/traps.c

@@ -35,7 +35,7 @@
 
 int show_unhandled_signals = 1;
 
-static DEFINE_SPINLOCK(die_lock);
+static DEFINE_RAW_SPINLOCK(die_lock);
 
 static int copy_code(struct pt_regs *regs, u16 *val, const u16 *insns)
 {
@@ -81,7 +81,7 @@ void die(struct pt_regs *regs, const char *str)
 
 	oops_enter();
 
-	spin_lock_irqsave(&die_lock, flags);
+	raw_spin_lock_irqsave(&die_lock, flags);
 	console_verbose();
 	bust_spinlocks(1);
 
@@ -100,7 +100,7 @@ void die(struct pt_regs *regs, const char *str)
 
 	bust_spinlocks(0);
 	add_taint(TAINT_DIE, LOCKDEP_NOW_UNRELIABLE);
-	spin_unlock_irqrestore(&die_lock, flags);
+	raw_spin_unlock_irqrestore(&die_lock, flags);
 	oops_exit();
 
 	if (in_interrupt())