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tools/memory-model: Remove out-of-date SRCU documentation

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Commit 6cd244c87428 ("tools/memory-model: Provide exact SRCU semantics")
changed the semantics of partially overlapping SRCU read-side critical
sections (among other things), making such documentation out-of-date.
The new, semantic changes are discussed in explanation.txt.  Remove the
out-of-date documentation.

Signed-off-by: Andrea Parri <parri.andrea@gmail.com>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit is contained in:
Andrea Parri 2023-03-23 02:37:51 +01:00 committed by Paul E. McKenney
parent 05dc8470b3
commit cc4a29819b
1 changed files with 1 additions and 26 deletions
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27
tools/memory-model/Documentation/litmus-tests.txt
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@ -1028,32 +1028,7 @@ Limitations of the Linux-kernel memory model (LKMM) include:
additional call_rcu() process to the site of the additional call_rcu() process to the site of the
emulated rcu-barrier(). emulated rcu-barrier().
e. Although sleepable RCU (SRCU) is now modeled, there e. Reader-writer locking is not modeled. It can be
are some subtle differences between its semantics and
those in the Linux kernel. For example, the kernel
might interpret the following sequence as two partially
overlapping SRCU read-side critical sections:
1 r1 = srcu_read_lock(&my_srcu);
2 do_something_1();
3 r2 = srcu_read_lock(&my_srcu);
4 do_something_2();
5 srcu_read_unlock(&my_srcu, r1);
6 do_something_3();
7 srcu_read_unlock(&my_srcu, r2);
In contrast, LKMM will interpret this as a nested pair of
SRCU read-side critical sections, with the outer critical
section spanning lines 1-7 and the inner critical section
spanning lines 3-5.
This difference would be more of a concern had anyone
identified a reasonable use case for partially overlapping
SRCU read-side critical sections. For more information
on the trickiness of such overlapping, please see:
https://paulmck.livejournal.com/40593.html
f. Reader-writer locking is not modeled. It can be
emulated in litmus tests using atomic read-modify-write emulated in litmus tests using atomic read-modify-write
operations. operations.