The patch titled
Documentation/volatile-considered-harmful.txt: correct cpu_relax() documentation
has been added to the -mm tree. Its filename is
documentation-volatile-considered-harmfultxt-correct-cpu_relax-documentation.patch
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Subject: Documentation/volatile-considered-harmful.txt: correct cpu_relax() documentation
From: Russell King <rmk@xxxxxxxxxxxxxxxx>
cpu_relax() is documented in volatile-considered-harmful.txt to be a
memory barrier. However, everyone with the exception of Blackfin and
possibly ia64 defines cpu_relax() to be a compiler barrier.
Make the documentation reflect the general concensus.
Signed-off-by: Russell King <rmk+kernel@xxxxxxxxxxxxxxxx>
Cc: <linux-arch@xxxxxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
Documentation/volatile-considered-harmful.txt | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff -puN Documentation/volatile-considered-harmful.txt~documentation-volatile-considered-harmfultxt-correct-cpu_relax-documentation Documentation/volatile-considered-harmful.txt
--- a/Documentation/volatile-considered-harmful.txt~documentation-volatile-considered-harmfultxt-correct-cpu_relax-documentation
+++ a/Documentation/volatile-considered-harmful.txt
@@ -63,9 +63,9 @@ way to perform a busy wait is:
cpu_relax();
The cpu_relax() call can lower CPU power consumption or yield to a
-hyperthreaded twin processor; it also happens to serve as a memory barrier,
-so, once again, volatile is unnecessary. Of course, busy-waiting is
-generally an anti-social act to begin with.
+hyperthreaded twin processor; it also happens to serve as a compiler
+barrier, so, once again, volatile is unnecessary. Of course, busy-
+waiting is generally an anti-social act to begin with.
There are still a few rare situations where volatile makes sense in the
kernel:
_
Patches currently in -mm which might be from rmk@xxxxxxxxxxxxxxxx are
origin.patch
documentation-volatile-considered-harmfultxt-correct-cpu_relax-documentation.patch
arm-convert-proc-cpu-aligment-to-seq_file.patch
arch-arm-include-asm-elfh-forward-declare-the-task-struct.patch
bitops-rename-for_each_bit-to-for_each_set_bit-mtd.patch
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