Subject: Re: [next-20220629] kobject warnings during boot

From: "Jason A. Donenfeld" <[email-masked]>
Date: Thu, 30 Jun 2022 13:55:45 +0200

Hi Sachin,

On Thu, Jun 30, 2022 at 05:01:57PM +0530, Sachin Sant wrote:
> [    0.000478] kobject: '(null)' ((____ptrval____)): is not initialized, yet kobject_get() is being called.
> [    0.002925] [c000000002a0fb30] [c00000000073b0bc] kobject_get+0x8c/0x100 (unreliable)
> [    0.003071] [c000000002a0fba0] [c00000000087e464] device_add+0xf4/0xb00
> [    0.003194] [c000000002a0fc80] [c000000000a7f6e4] of_device_add+0x64/0x80
> [    0.003321] [c000000002a0fcb0] [c000000000a800d0] of_platform_device_create_pdata+0xd0/0x1b0
> [    0.003476] [c000000002a0fd00] [c00000000201fa44] pnv_get_random_long_early+0x240/0x2e4
> [    0.003623] [c000000002a0fe20] [c000000002060c38] random_init+0xc0/0x214

Huh, that's a surprise, because random_init() is being called long after
all of the arch-specific stuff is initialized. This might point to
something else fishy happening during ppc's init? Or maybe the of device
needs a parent that hasn't been initialized yet. Not sure... But see if
the below patch fixes the issue. I don't have a POWER8 machine to try
this on, but if it works for you, I'll build it into a real patch.

Jason

diff --git a/arch/powerpc/platforms/powernv/rng.c b/arch/powerpc/platforms/powernv/rng.c
index 463c78c52cc5..bd5ad5f351c2 100644
--- a/arch/powerpc/platforms/powernv/rng.c
+++ b/arch/powerpc/platforms/powernv/rng.c
@@ -176,12 +176,8 @@ static int __init pnv_get_random_long_early(unsigned long *v)
 		    NULL) != pnv_get_random_long_early)
 		return 0;

-	for_each_compatible_node(dn, NULL, "ibm,power-rng") {
-		if (rng_create(dn))
-			continue;
-		/* Create devices for hwrng driver */
-		of_platform_device_create(dn, NULL, NULL);
-	}
+	for_each_compatible_node(dn, NULL, "ibm,power-rng")
+		rng_create(dn);

 	if (!ppc_md.get_random_seed)
 		return 0;
@@ -205,10 +201,16 @@ void __init pnv_rng_init(void)

 static int __init pnv_rng_late_init(void)
 {
+	struct device_node *dn;
 	unsigned long v;
+
 	/* In case it wasn't called during init for some other reason. */
 	if (ppc_md.get_random_seed == pnv_get_random_long_early)
 		pnv_get_random_long_early(&v);
+	if (ppc_md.get_random_seed == powernv_get_random_long) {
+		for_each_compatible_node(dn, NULL, "ibm,power-rng")
+			of_platform_device_create(dn, NULL, NULL);
+	}
 	return 0;
 }
 machine_subsys_initcall(powernv, pnv_rng_late_init);