Why is arch/x86/kernel/acpi/sleep.c:temp_stack 10k?

PATCH In review Matt Mackall 5 participants 9 messages Oct 1, 2008 – Oct 9, 2008

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x86 ACPI Suspend to RAM

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Matt Mackall

author

2008-10-01 00:15 UTC #0 lore raw

We've got:

#if defined(CONFIG_SMP) && defined(CONFIG_64BIT)
static char temp_stack[10240];
#endif

and:

#ifdef CONFIG_SMP
        stack_start.sp = temp_stack + 4096;

#endif

..which suggests we use at most 4k of the stack?

Signature · 1 line

Mathematics is the supreme nostalgia of our time.

Pavel Machek

2008-10-09 08:56 UTC #1 lore raw

Quoted 7 lines

We've got:
#if defined(CONFIG_SMP) && defined(CONFIG_64BIT)
static char temp_stack[10240];
#endif

Quoted 7 lines

and:
#ifdef CONFIG_SMP
        stack_start.sp = temp_stack + 4096;
#endif
..which suggests we use at most 4k of the stack?

I guess someone (probably me) was "playing it safe" -- not exactly remembering if stack grows down or up. I guess it should be safe to change it... will do that.
Pavel

Signature · 2 lines

(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

Matt Mackall

author

2008-10-09 16:58 UTC #2 lore raw

PATCH 1/1 x86: trim ACPI sleep stack buffer

Quoted 12 lines · Pavel Machek

Quoted 12 lines
We've got:
#if defined(CONFIG_SMP) && defined(CONFIG_64BIT)
static char temp_stack[10240];
#endif
and:
#ifdef CONFIG_SMP
        stack_start.sp = temp_stack + 4096;
#endif

Quoted 6 lines

Quoted 1 line
..which suggests we use at most 4k of the stack?
I guess someone (probably me) was "playing it safe" -- not exactly remembering if stack grows down or up. I guess it should be safe to change it... will do that.
Pavel

I've already got a patch, I was just wondering if there was some obscure architectural reason for it that I wasn't aware of.

x86: trim ACPI sleep stack buffer

x86_64 SMP suspend to RAM uses a 10k temporary stack for saving the kernel state, but only 4k of it is used. Shrink it to 4k.

Signed-off-by Matt Mackall <[email protected]>

arch/x86/kernel/acpi/sleep.c +1 -1

diff -r 73d55a1b6c10 arch/x86/kernel/acpi/sleep.c
@@ -21,7 +21,7 @@
 static unsigned long acpi_realmode;
 
 #if defined(CONFIG_SMP) && defined(CONFIG_64BIT)
-static char temp_stack[10240];
+static char temp_stack[4096];
 #endif
 
 /**

Signature · 1 line

Mathematics is the supreme nostalgia of our time.

Len Brown

reviewer

2008-10-09 17:19 UTC #3 lore raw

Re: [PATCH] x86: trim ACPI sleep stack buffer

applied to acpi-test.

thanks Matt,
-Len

Quoted 52 lines · Matt Mackall

Quoted 12 lines · Pavel Machek
Quoted 12 lines
We've got:
#if defined(CONFIG_SMP) && defined(CONFIG_64BIT)
static char temp_stack[10240];
#endif
and:
#ifdef CONFIG_SMP
        stack_start.sp = temp_stack + 4096;
#endif
Quoted 6 lines
Quoted 1 line
..which suggests we use at most 4k of the stack?
I guess someone (probably me) was "playing it safe" -- not exactly remembering if stack grows down or up. I guess it should be safe to change it... will do that.
Pavel
I've already got a patch, I was just wondering if there was some obscure architectural reason for it that I wasn't aware of.
x86: trim ACPI sleep stack buffer
x86_64 SMP suspend to RAM uses a 10k temporary stack for saving the kernel state, but only 4k of it is used. Shrink it to 4k.
Signed-off-by Matt Mackall <[email protected]>
diff -r 73d55a1b6c10 arch/x86/kernel/acpi/sleep.c
arch/x86/kernel/acpi/sleep.c +1 -1
@@ -21,7 +21,7 @@
 static unsigned long acpi_realmode;
 
 #if defined(CONFIG_SMP) && defined(CONFIG_64BIT)
-static char temp_stack[10240];
+static char temp_stack[4096];
 #endif
 
 /**
Signature · 7 lines
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Moore, Robert

2008-10-09 17:24 UTC #4 lore raw

RE: [PATCH] x86: trim ACPI sleep stack buffer

Sounds like you need a

#define DEFAULT_STACK_SIZE 4096

Somewhere.

Quoted 73 lines

-----Original Message-----
From: [email protected] [mailto:linux-acpi- [email protected]] On Behalf Of Len Brown
Sent: Thursday, October 09, 2008 10:20 AM
To: Matt Mackall
Cc: Pavel Machek; Ingo Molnar; Linux Kernel Mailing List; linux- [email protected]
Subject: Re: [PATCH] x86: trim ACPI sleep stack buffer
applied to acpi-test.
thanks Matt,
-Len
Quoted 13 lines · Matt Mackall
Quoted 12 lines · Pavel Machek
Quoted 12 lines
We've got:
#if defined(CONFIG_SMP) && defined(CONFIG_64BIT)
static char temp_stack[10240];
#endif
and:
#ifdef CONFIG_SMP
        stack_start.sp = temp_stack + 4096;
#endif
Quoted 6 lines
Quoted 6 lines
Quoted 1 line
..which suggests we use at most 4k of the stack?
I guess someone (probably me) was "playing it safe" -- not exactly remembering if stack grows down or up. I guess it should be safe to change it... will do that.
Pavel
Quoted 28 lines
I've already got a patch, I was just wondering if there was some obscure architectural reason for it that I wasn't aware of.
x86: trim ACPI sleep stack buffer
x86_64 SMP suspend to RAM uses a 10k temporary stack for saving the kernel state, but only 4k of it is used. Shrink it to 4k.
Signed-off-by Matt Mackall <[email protected]>
diff -r 73d55a1b6c10 arch/x86/kernel/acpi/sleep.c
arch/x86/kernel/acpi/sleep.c Thu Oct 09 11:51:54 2008 -0500 renamed from arch/x86/kernel/acpi/sleep.c Wed Oct 08 14:48:45 2008 -0500 +1 -2
@@ -21,7 +21,7 @@
 static unsigned long acpi_realmode;
 
 #if defined(CONFIG_SMP) && defined(CONFIG_64BIT)
-static char temp_stack[10240];
+static char temp_stack[4096];
 #endif
 
 /**
 
--
Mathematics is the supreme nostalgia of our time.
Quoted 5 lines
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Matt Mackall

author

2008-10-09 17:44 UTC #5 lore raw

RE: [PATCH] x86: trim ACPI sleep stack buffer

Quoted 5 lines · Robert

Sounds like you need a
#define DEFAULT_STACK_SIZE 4096
Somewhere.

Or maybe something like this:

x86: remove magic number from ACPI sleep stack buffer

Signed-off-by Matt Mackall <[email protected]>

arch/x86/kernel/acpi/sleep.c +1 -1

diff -r 375a00b8bf10 arch/x86/kernel/acpi/sleep.c
@@ -97,7 +97,7 @@
 #else /* CONFIG_64BIT */
 	header->trampoline_segment = setup_trampoline() >> 4;
 #ifdef CONFIG_SMP
-	stack_start.sp = temp_stack + 4096;
+	stack_start.sp = temp_stack + sizeof(temp_stack);
 #endif
 	initial_code = (unsigned long)wakeup_long64;
 	saved_magic = 0x123456789abcdef0;

Signature · 1 line

Mathematics is the supreme nostalgia of our time.

Pavel Machek

Acked-by

2008-10-09 18:06 UTC #6 lore raw

Re: [PATCH] x86: trim ACPI sleep stack buffer

Quoted 5 lines · Matt Mackall

Quoted 4 lines · Robert
Sounds like you need a
#define DEFAULT_STACK_SIZE 4096

Quoted 8 lines

Quoted 1 line
Somewhere.
Or maybe something like this:
x86: remove magic number from ACPI sleep stack buffer
Signed-off-by Matt Mackall <[email protected]>

Acked-by Pavel Machek <[email protected]>

Quoted 14 lines

diff -r 375a00b8bf10 arch/x86/kernel/acpi/sleep.c

arch/x86/kernel/acpi/sleep.c +1 -1

@@ -97,7 +97,7 @@
 #else /* CONFIG_64BIT */
 	header->trampoline_segment = setup_trampoline() >> 4;
 #ifdef CONFIG_SMP
-	stack_start.sp = temp_stack + 4096;
+	stack_start.sp = temp_stack + sizeof(temp_stack);
 #endif
 	initial_code = (unsigned long)wakeup_long64;
 	saved_magic = 0x123456789abcdef0;

Signature · 2 lines

(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

Len Brown

reviewer

2008-10-09 18:35 UTC #7 lore raw

Re: [PATCH] x86: trim ACPI sleep stack buffer

applied (before the stack change patch:-) to acpi-test

thanks,
-Len

Quoted 36 lines · Pavel Machek

Quoted 5 lines · Matt Mackall
Quoted 4 lines · Robert
Sounds like you need a
#define DEFAULT_STACK_SIZE 4096
Quoted 8 lines
Quoted 1 line
Somewhere.
Or maybe something like this:
x86: remove magic number from ACPI sleep stack buffer
Signed-off-by Matt Mackall <[email protected]>
Acked-by Pavel Machek <[email protected]>
Quoted 14 lines
diff -r 375a00b8bf10 arch/x86/kernel/acpi/sleep.c
arch/x86/kernel/acpi/sleep.c +1 -1
@@ -97,7 +97,7 @@
 #else /* CONFIG_64BIT */
 	header->trampoline_segment = setup_trampoline() >> 4;
 #ifdef CONFIG_SMP
-	stack_start.sp = temp_stack + 4096;
+	stack_start.sp = temp_stack + sizeof(temp_stack);
 #endif
 	initial_code = (unsigned long)wakeup_long64;
 	saved_magic = 0x123456789abcdef0;
Signature · 2 lines
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

Rafael J. Wysocki

2008-10-09 21:21 UTC #8 lore raw

Re: [PATCH] x86: trim ACPI sleep stack buffer

Quoted 1 line · Len Brown

applied (before the stack change patch:-) to acpi-test

FWIW, I had a look at it, looks good.

Thanks,
Rafael

Quoted 44 lines · Pavel Machek

Quoted 18 lines · Matt Mackall
Quoted 5 lines · Robert
Quoted 4 lines
Sounds like you need a
#define DEFAULT_STACK_SIZE 4096
Quoted 8 lines
Quoted 1 line
Somewhere.
Or maybe something like this:
x86: remove magic number from ACPI sleep stack buffer
Signed-off-by Matt Mackall <[email protected]>
Acked-by Pavel Machek <[email protected]>
Quoted 19 lines
Quoted 14 lines
diff -r 375a00b8bf10 arch/x86/kernel/acpi/sleep.c
arch/x86/kernel/acpi/sleep.c +1 -1
@@ -97,7 +97,7 @@
 #else /* CONFIG_64BIT */
 	header->trampoline_segment = setup_trampoline() >> 4;
 #ifdef CONFIG_SMP
-	stack_start.sp = temp_stack + 4096;
+	stack_start.sp = temp_stack + sizeof(temp_stack);
 #endif
 	initial_code = (unsigned long)wakeup_long64;
 	saved_magic = 0x123456789abcdef0;
Signature · 2 lines
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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