overview of bust_spinlocks

[manty kuma <mantykuma@xxxxxxxxx>]

What is the concept of bust_spinlocks()

In do_kernel_fault() function of ARM 64, we can see the following code

https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/arch/arm64/mm/fault.c?id=refs/tags/v3.19#n85

static void __do_kernel_fault(struct mm_struct *mm, unsigned long addr,
			      unsigned int esr, struct pt_regs *regs)
{
	/*
	 * Are we prepared to handle this kernel fault?
	 */
	if (fixup_exception(regs))
		return;

	/*
	 * No handler, we'll have to terminate things with extreme prejudice.
	 */
	bust_spinlocks(1);
	pr_alert("Unable to handle kernel %s at virtual address %08lx\n",
		 (addr < PAGE_SIZE) ? "NULL pointer dereference" :
		 "paging request", addr);

	show_pte(mm, addr);
	die("Oops", regs, esr);
	bust_spinlocks(0);
	do_exit(SIGKILL);
}

I have looked into its definition. It is as follows:

void __attribute__((weak)) bust_spinlocks(int yes)
{
	if (yes) {
		++oops_in_progress;
	} else {
#ifdef CONFIG_VT
		unblank_screen();
#endif
		console_unblank();
		if (--oops_in_progress == 0)
			wake_up_klogd();
	}
}

So basically when i am saying bust_spinlocks(1), it is just incrementing the oops)_in_progress variable. How is it serving the purposr of a lock here?

Best Regards,

Manty

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