[PATCH v2] irqflags: fix (at least latent) code generation issue

[PATCH v2] irqflags: fix (at least latent) code generation issue

[Jan Beulich]

The conditional in local_irq_restore() otherwise can cause code bloat
(the if and else blocks may get translated into separate code paths
despite the generated code being identical, dependent on compiler
internal heuristics). Note that this adjustment gets the code in sync
with the comment preceding it (which was slightly wrong from at least
from 2.6.37 onwards).

The code bloat was observed in reality with an experimental x86 patch.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
---
v2: Deal with architectures not defining raw_irqs_disabled() by
    retaining the CONFIG_TRACE_IRQFLAGS_SUPPORT-dependent
    implementations of irqs_disabled(). Move out of either conditional
    the already identical definitions of local_save_flags() and
    irqs_disabled_flags().
---
 include/linux/irqflags.h |   43 ++++++++++++++++++++++---------------------
 1 file changed, 22 insertions(+), 21 deletions(-)

--- 3.19-rc5/include/linux/irqflags.h
+++ 3.19-rc5-irqflags/include/linux/irqflags.h
@@ -85,7 +85,7 @@
  * The local_irq_*() APIs are equal to the raw_local_irq*()
  * if !TRACE_IRQFLAGS.
  */
-#ifdef CONFIG_TRACE_IRQFLAGS_SUPPORT
+#ifdef CONFIG_TRACE_IRQFLAGS
 #define local_irq_enable() \
 	do { trace_hardirqs_on(); raw_local_irq_enable(); } while (0)
 #define local_irq_disable() \
@@ -107,22 +107,6 @@
 			raw_local_irq_restore(flags);	\
 		}					\
 	} while (0)
-#define local_save_flags(flags)				\
-	do {						\
-		raw_local_save_flags(flags);		\
-	} while (0)
-
-#define irqs_disabled_flags(flags)			\
-	({						\
-		raw_irqs_disabled_flags(flags);		\
-	})
-
-#define irqs_disabled()					\
-	({						\
-		unsigned long _flags;			\
-		raw_local_save_flags(_flags);		\
-		raw_irqs_disabled_flags(_flags);	\
-	})
 
 #define safe_halt()				\
 	do {					\
@@ -131,7 +115,7 @@
 	} while (0)
 
 
-#else /* !CONFIG_TRACE_IRQFLAGS_SUPPORT */
+#else /* !CONFIG_TRACE_IRQFLAGS */
 
 #define local_irq_enable()	do { raw_local_irq_enable(); } while (0)
 #define local_irq_disable()	do { raw_local_irq_disable(); } while (0)
@@ -140,11 +124,28 @@
 		raw_local_irq_save(flags);			\
 	} while (0)
 #define local_irq_restore(flags) do { raw_local_irq_restore(flags); } while (0)
-#define local_save_flags(flags)	do { raw_local_save_flags(flags); } while (0)
-#define irqs_disabled()		(raw_irqs_disabled())
-#define irqs_disabled_flags(flags) (raw_irqs_disabled_flags(flags))
 #define safe_halt()		do { raw_safe_halt(); } while (0)
 
+#endif /* CONFIG_TRACE_IRQFLAGS */
+
+#define local_save_flags(flags)	raw_local_save_flags(flags)
+
+/*
+ * Some architectures don't define arch_irqs_disabled(), so even if either
+ * definition would be fine we need to use different ones for the time being
+ * to avoid build issues.
+ */
+#ifdef CONFIG_TRACE_IRQFLAGS_SUPPORT
+#define irqs_disabled()					\
+	({						\
+		unsigned long _flags;			\
+		raw_local_save_flags(_flags);		\
+		raw_irqs_disabled_flags(_flags);	\
+	})
+#else /* !CONFIG_TRACE_IRQFLAGS_SUPPORT */
+#define irqs_disabled()	raw_irqs_disabled()
 #endif /* CONFIG_TRACE_IRQFLAGS_SUPPORT */
 
+#define irqs_disabled_flags(flags) raw_irqs_disabled_flags(flags)
+
 #endif

[tip:irq/core] irqflags: Fix (at least latent) code generation issue

[tip-bot for Jan Beulich]

Commit-ID:  db2dcb4f91d5fec5c346a82c309187ee821e2495
Gitweb:     http://git.kernel.org/tip/db2dcb4f91d5fec5c346a82c309187ee821e2495
Author:     Jan Beulich <JBeulich@suse.com>
AuthorDate: Tue, 20 Jan 2015 13:00:46 +0000
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Thu, 19 Feb 2015 01:08:42 +0100

irqflags: Fix (at least latent) code generation issue

The conditional in local_irq_restore() otherwise can cause code
bloat (the if and else blocks may get translated into separate
code paths despite the generated code being identical, dependent
on compiler internal heuristics). Note that this adjustment gets
the code in sync with the comment preceding it (which was
slightly wrong from at least from 2.6.37 onwards).

The code bloat was observed in reality with an experimental x86
patch.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/54BE5F8E02000078000570A7@mail.emea.novell.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 include/linux/irqflags.h | 43 ++++++++++++++++++++++---------------------
 1 file changed, 22 insertions(+), 21 deletions(-)

diff --git a/include/linux/irqflags.h b/include/linux/irqflags.h
index d176d65..5dd1272 100644
--- a/include/linux/irqflags.h
+++ b/include/linux/irqflags.h
@@ -85,7 +85,7 @@
  * The local_irq_*() APIs are equal to the raw_local_irq*()
  * if !TRACE_IRQFLAGS.
  */
-#ifdef CONFIG_TRACE_IRQFLAGS_SUPPORT
+#ifdef CONFIG_TRACE_IRQFLAGS
 #define local_irq_enable() \
 	do { trace_hardirqs_on(); raw_local_irq_enable(); } while (0)
 #define local_irq_disable() \
@@ -107,22 +107,6 @@
 			raw_local_irq_restore(flags);	\
 		}					\
 	} while (0)
-#define local_save_flags(flags)				\
-	do {						\
-		raw_local_save_flags(flags);		\
-	} while (0)
-
-#define irqs_disabled_flags(flags)			\
-	({						\
-		raw_irqs_disabled_flags(flags);		\
-	})
-
-#define irqs_disabled()					\
-	({						\
-		unsigned long _flags;			\
-		raw_local_save_flags(_flags);		\
-		raw_irqs_disabled_flags(_flags);	\
-	})
 
 #define safe_halt()				\
 	do {					\
@@ -131,7 +115,7 @@
 	} while (0)
 
 
-#else /* !CONFIG_TRACE_IRQFLAGS_SUPPORT */
+#else /* !CONFIG_TRACE_IRQFLAGS */
 
 #define local_irq_enable()	do { raw_local_irq_enable(); } while (0)
 #define local_irq_disable()	do { raw_local_irq_disable(); } while (0)
@@ -140,11 +124,28 @@
 		raw_local_irq_save(flags);			\
 	} while (0)
 #define local_irq_restore(flags) do { raw_local_irq_restore(flags); } while (0)
-#define local_save_flags(flags)	do { raw_local_save_flags(flags); } while (0)
-#define irqs_disabled()		(raw_irqs_disabled())
-#define irqs_disabled_flags(flags) (raw_irqs_disabled_flags(flags))
 #define safe_halt()		do { raw_safe_halt(); } while (0)
 
+#endif /* CONFIG_TRACE_IRQFLAGS */
+
+#define local_save_flags(flags)	raw_local_save_flags(flags)
+
+/*
+ * Some architectures don't define arch_irqs_disabled(), so even if either
+ * definition would be fine we need to use different ones for the time being
+ * to avoid build issues.
+ */
+#ifdef CONFIG_TRACE_IRQFLAGS_SUPPORT
+#define irqs_disabled()					\
+	({						\
+		unsigned long _flags;			\
+		raw_local_save_flags(_flags);		\
+		raw_irqs_disabled_flags(_flags);	\
+	})
+#else /* !CONFIG_TRACE_IRQFLAGS_SUPPORT */
+#define irqs_disabled()	raw_irqs_disabled()
 #endif /* CONFIG_TRACE_IRQFLAGS_SUPPORT */
 
+#define irqs_disabled_flags(flags) raw_irqs_disabled_flags(flags)
+
 #endif