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Disable CONFIG_CONSTRUCTORS when not needed by CONFIG_GCOV_KERNEL

PATCH In review Josh Triplett 3 participants 5 messages Jun 5, 2011 – Jun 7, 2011 Gcov based kernel profiling

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Josh Triplett

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#0 lore raw

PATCH 1/1 Disable CONFIG_CONSTRUCTORS when not needed by CONFIG_GCOV_KERNEL

CONFIG_CONSTRUCTORS controls support for running constructor functions at kernel init time. According to commit b99b87f70c7785ab1e253c6220f4b0b57ce3a7f7, gcov (CONFIG_GCOV_KERNEL) needs this. However, CONFIG_CONSTRUCTORS currently defaults to y, with no option to disable it, and CONFIG_GCOV_KERNEL depends on it. Instead, default it to n and have CONFIG_GCOV_KERNEL select it, so that the normal case of CONFIG_GCOV_KERNEL=n will result in CONFIG_CONSTRUCTORS=n.

Observed in the short list of =y values in a minimal kernel configuration.

Signed-off-by Josh Triplett <[email protected]>

---
CCing people copied on the original commit
b99b87f70c7785ab1e253c6220f4b0b57ce3a7f7.

 init/Kconfig        |    1 -
 kernel/gcov/Kconfig |    3 ++-
 2 files changed, 2 insertions(+), 2 deletions(-)
init/Kconfig +0 -1
index ebafac4..e9bf65f 100644
@@ -19,7 +19,6 @@ config DEFCONFIG_LIST
 config CONSTRUCTORS
 	bool
 	depends on !UML
-	default y
 
 config HAVE_IRQ_WORK
 	bool
kernel/gcov/Kconfig +2 -1
index b8cadf7..5bf924d 100644
@@ -2,7 +2,8 @@ menu "GCOV-based kernel profiling"
 
 config GCOV_KERNEL
 	bool "Enable gcov-based kernel profiling"
-	depends on DEBUG_FS && CONSTRUCTORS
+	depends on DEBUG_FS
+	select CONSTRUCTORS
 	default n
 	---help---
 	This option enables gcov-based code profiling (e.g. for code coverage
Signature · 1 line
1.7.5.3
Acked-by on v1 1/1
#1 lore raw
Quoted 9 lines · Josh Triplett

CONFIG_CONSTRUCTORS controls support for running constructor functions at kernel init time. According to commit b99b87f70c7785ab1e253c6220f4b0b57ce3a7f7, gcov (CONFIG_GCOV_KERNEL) needs this. However, CONFIG_CONSTRUCTORS currently defaults to y, with no option to disable it, and CONFIG_GCOV_KERNEL depends on it. Instead, default it to n and have CONFIG_GCOV_KERNEL select it, so that the normal case of CONFIG_GCOV_KERNEL=n will result in CONFIG_CONSTRUCTORS=n.

Quoted 5 lines

Observed in the short list of =y values in a minimal kernel configuration.

Signed-off-by Josh Triplett<[email protected]>

---

I tested this patch and GCOV profiling still works with it applied. To my knowledge, GCOV profiling is the only kernel mechanism using GCC's constructors and this may save some bytes.

Acked-by Peter Oberparleiter <[email protected]>

Regards,
Peter

author
#2 lore raw
Quoted 13 lines · Peter Oberparleiter
Quoted 12 lines · Josh Triplett

CONFIG_CONSTRUCTORS controls support for running constructor functions at kernel init time. According to commit b99b87f70c7785ab1e253c6220f4b0b57ce3a7f7, gcov (CONFIG_GCOV_KERNEL) needs this. However, CONFIG_CONSTRUCTORS currently defaults to y, with no option to disable it, and CONFIG_GCOV_KERNEL depends on it. Instead, default it to n and have CONFIG_GCOV_KERNEL select it, so that the normal case of CONFIG_GCOV_KERNEL=n will result in CONFIG_CONSTRUCTORS=n.

Observed in the short list of =y values in a minimal kernel configuration.

Quoted 8 lines
Quoted 2 lines
Signed-off-by Josh Triplett<[email protected]>

---

I tested this patch and GCOV profiling still works with it applied. To my knowledge, GCOV profiling is the only kernel mechanism using GCC's constructors and this may save some bytes.

Acked-by Peter Oberparleiter <[email protected]>

Excellent, thanks for testing and acking.

What tree should this patch go through?

- Josh Triplett

#3 lore raw
Quoted 21 lines · Josh Triplett
Quoted 20 lines · Peter Oberparleiter
Quoted 9 lines · Josh Triplett

CONFIG_CONSTRUCTORS controls support for running constructor functions at kernel init time.  According to commit b99b87f70c7785ab1e253c6220f4b0b57ce3a7f7, gcov (CONFIG_GCOV_KERNEL) needs this.  However, CONFIG_CONSTRUCTORS currently defaults to y, with no option to disable it, and CONFIG_GCOV_KERNEL depends on it.  Instead, default it to n and have CONFIG_GCOV_KERNEL select it, so that the normal case of CONFIG_GCOV_KERNEL=n will result in CONFIG_CONSTRUCTORS=n.

Quoted 5 lines

Observed in the short list of =y values in a minimal kernel configuration.

Signed-off-by Josh Triplett<[email protected]>

---

I tested this patch and GCOV profiling still works with it applied. To my knowledge, GCOV profiling is the only kernel mechanism using GCC's constructors and this may save some bytes.

Quoted 6 lines
Quoted 1 line
Acked-by Peter Oberparleiter <[email protected]>

Excellent, thanks for testing and acking.

What tree should this patch go through?

Andrew is supposed to take this. :)

Acked-by on v1 1/1
#4 lore raw
In reply to Josh Triplett
Quoted 9 lines · Josh Triplett

CONFIG_CONSTRUCTORS controls support for running constructor functions at kernel init time.  According to commit b99b87f70c7785ab1e253c6220f4b0b57ce3a7f7, gcov (CONFIG_GCOV_KERNEL) needs this.  However, CONFIG_CONSTRUCTORS currently defaults to y, with no option to disable it, and CONFIG_GCOV_KERNEL depends on it.  Instead, default it to n and have CONFIG_GCOV_KERNEL select it, so that the normal case of CONFIG_GCOV_KERNEL=n will result in CONFIG_CONSTRUCTORS=n.

Quoted 4 lines

Observed in the short list of =y values in a minimal kernel configuration.

Signed-off-by Josh Triplett <[email protected]>

Yeah, this is reasonable, so,

Acked-by WANG Cong <[email protected]>

Thanks!