Re: maxcpus=1 broken, ACPI bug?

[Linus Torvalds <torvalds@osdl.org>]

On Thu, 17 Nov 2005, Maneesh Soni wrote:
> 
> Using maxcpus=1 boot option, hangs the system while booting. It was
> working till 2.6.13-rc2. After git bisect I found that after backing
> out this ACPI patch it works again, though I had to manually sort the
> reject while backing out.
> 
> http://www.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=acf05f4b7f558051ea0028e8e617144123650272

Hmm. That patch had a totally idiotic thinko in it (look at the for-loop 
in acpi_processor_get_power_info_default() and notice how it doesn't 
actually change anything in the loop).

That thinko was later fixed (albeit in a really stupid way, and the same 
cut-and-paste bug still exists in acpi_processor_get_power_info_fadt()).

Anyway, can you test this diff? It

 (a) removes the insane (and in one case incorrect) memset loop
 (b) makes the code that sets "pr->flags.power = 1" match the comment and 
     the previous behaviour.

Does that make a difference?

		Linus

---
diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
index 573b6a9..2445828 100644
--- a/drivers/acpi/processor_idle.c
+++ b/drivers/acpi/processor_idle.c
@@ -524,8 +524,7 @@ static int acpi_processor_get_power_info
 	if (!pr->pblk)
 		return_VALUE(-ENODEV);
 
-	for (i = 0; i < ACPI_PROCESSOR_MAX_POWER; i++)
-		memset(pr->power.states, 0, sizeof(struct acpi_processor_cx));
+	memset(pr->power.states, 0, sizeof(pr->power.states));
 
 	/* if info is obtained from pblk/fadt, type equals state */
 	pr->power.states[ACPI_STATE_C1].type = ACPI_STATE_C1;
@@ -559,9 +558,7 @@ static int acpi_processor_get_power_info
 
 	ACPI_FUNCTION_TRACE("acpi_processor_get_power_info_default_c1");
 
-	for (i = 0; i < ACPI_PROCESSOR_MAX_POWER; i++)
-		memset(&(pr->power.states[i]), 0,
-		       sizeof(struct acpi_processor_cx));
+	memset(pr->power.states, 0, sizeof(pr->power.states));
 
 	/* if info is obtained from pblk/fadt, type equals state */
 	pr->power.states[ACPI_STATE_C1].type = ACPI_STATE_C1;
@@ -873,7 +870,8 @@ static int acpi_processor_get_power_info
 	for (i = 1; i < ACPI_PROCESSOR_MAX_POWER; i++) {
 		if (pr->power.states[i].valid) {
 			pr->power.count = i;
-			pr->flags.power = 1;
+			if (pr->power.states[i].type >= ACPI_STATE_C2)
+				pr->flags.power = 1;
 		}
 	}
 
-
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