Messages in this thread Patch in this message | | | Date | Tue, 9 Mar 2010 16:30:24 +0000 | From | Russell King <> | Subject | [RFC:PATCH] Correct cpu_relax() documentation |
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Subject: Correct cpu_relax() documentation
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@arm.linux.org.uk> --- Documentation/volatile-considered-harmful.txt | 6 +++--- 1 files changed, 3 insertions(+), 3 deletions(-)
diff --git a/Documentation/volatile-considered-harmful.txt b/Documentation/volatile-considered-harmful.txt index 991c26a..db0cb22 100644 --- a/Documentation/volatile-considered-harmful.txt +++ b/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:
-- Russell King Linux kernel 2.6 ARM Linux - http://www.arm.linux.org.uk/ maintainer of:
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