Re: [PATCH RFC V6 2/11] x86/ticketlock: don't inline _spin_unlock when using paravirt spinlocks

On Wed, Mar 21, 2012 at 3:21 AM, Raghavendra K T
[off-list ref] wrote:

Ugh. This is getting really ugly.

Can we just fix it by
 - getting rid of INLINE_SPIN_UNLOCK entirely

 - replacing it with UNINLINE_SPIN_UNLOCK instead with the reverse
meaning, and no "def_bool" at all, just a simple

        config UNINLINE_SPIN_UNLOCK
                bool

 - make the various people who want to uninline the spinlocks (like
spinlock debugging, paravirt etc) all just do

        select UNINLINE_SPIN_UNLOCK

because quite frankly, the whole spinunlock inlining logic is
*already* unreadable, and you just made it worse.

                      Linus

On 03/21/2012 10:43 PM, Linus Torvalds wrote:

On Wed, Mar 21, 2012 at 3:21 AM, Raghavendra K T
[off-list ref]  wrote:

quoted

From: Jeremy Fitzhardinge<redacted>

The code size expands somewhat, and its probably better to just call
a function rather than inline it.

Signed-off-by: Jeremy Fitzhardinge<redacted>
Signed-off-by: Raghavendra K T<redacted>
---
  arch/x86/Kconfig     |    3 +++
  kernel/Kconfig.locks |    2 +-
  2 files changed, 4 insertions(+), 1 deletions(-)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 5bed94e..10c28ec 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig

@@ -623,6 +623,9 @@ config PARAVIRT_SPINLOCKS

          If you are unsure how to answer this question, answer N.

+config ARCH_NOINLINE_SPIN_UNLOCK
+       def_bool PARAVIRT_SPINLOCKS
+
  config PARAVIRT_CLOCK
        bool

diff --git a/kernel/Kconfig.locks b/kernel/Kconfig.locks
index 5068e2a..584637b 100644
--- a/kernel/Kconfig.locks
+++ b/kernel/Kconfig.locks

@@ -125,7 +125,7 @@ config INLINE_SPIN_LOCK_IRQSAVE
                 ARCH_INLINE_SPIN_LOCK_IRQSAVE

  config INLINE_SPIN_UNLOCK
-       def_bool !DEBUG_SPINLOCK&&  (!PREEMPT || ARCH_INLINE_SPIN_UNLOCK)
+       def_bool !DEBUG_SPINLOCK&&  (!PREEMPT || ARCH_INLINE_SPIN_UNLOCK)&&  !ARCH_NOINLINE_SPIN_UNLOCK

  config INLINE_SPIN_UNLOCK_BH
        def_bool !DEBUG_SPINLOCK&&  ARCH_INLINE_SPIN_UNLOCK_BH

3 more quoted lines

Agree that it had become longer.

Can we just fix it by
  - getting rid of INLINE_SPIN_UNLOCK entirely

  - replacing it with UNINLINE_SPIN_UNLOCK instead with the reverse
meaning, and no "def_bool" at all, just a simple

         config UNINLINE_SPIN_UNLOCK
                 bool

  - make the various people who want to uninline the spinlocks (like
spinlock debugging, paravirt etc) all just do

         select UNINLINE_SPIN_UNLOCK

I just posted  https://lkml.org/lkml/2012/3/22/94. Please let me know
if that looks better.
And this patch should now become something like
---

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 5bed94e..2666b7d 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig

@@ -613,6 +613,7 @@ config PARAVIRT
 config PARAVIRT_SPINLOCKS

	 bool "Paravirtualization layer for spinlocks"
	 depends on PARAVIRT && SMP && EXPERIMENTAL
+	 select UNINLINE_SPIN_UNLOCK
	 ---help---
	   Paravirtualized spinlocks allow a pvops backend to replace the
	   spinlock implementation with something virtualization-friendly