diff options
author | Paul E. McKenney <[email protected]> | 2016-06-15 16:08:17 -0700 |
---|---|---|
committer | Ingo Molnar <[email protected]> | 2016-06-17 09:54:45 +0200 |
commit | ebff09a6ff164aec2b33bf1f9a488c45ac108413 (patch) | |
tree | 4c2e43caeacbd254daa8439564e991b1de82750c /tools/perf/scripts/python/call-graph-from-postgresql.py | |
parent | b316ff783d17bd6217804e2e4385ce9347d7dad9 (diff) |
locking/Documentation: Clarify limited control-dependency scope
Nothing in the control-dependencies section of memory-barriers.txt
says that control dependencies don't extend beyond the end of the
if-statement containing the control dependency. Worse yet, in many
situations, they do extend beyond that if-statement. In particular,
the compiler cannot destroy the control dependency given proper use of
READ_ONCE() and WRITE_ONCE(). However, a weakly ordered system having
a conditional-move instruction provides the control-dependency guarantee
only to code within the scope of the if-statement itself.
This commit therefore adds words and an example demonstrating this
limitation of control dependencies.
Reported-by: Will Deacon <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>
Acked-by: Peter Zijlstra (Intel) <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>
Diffstat (limited to 'tools/perf/scripts/python/call-graph-from-postgresql.py')
0 files changed, 0 insertions, 0 deletions