rcu: Inform KCSAN of one-byte cmpxchg() in rcu_trc_cmpxchg_need_qs()

Browse source

Tasks Trace RCU needs a single-byte cmpxchg(), but no such thing exists.
Therefore, rcu_trc_cmpxchg_need_qs() emulates one using field substitution
and a four-byte cmpxchg(), such that the other three bytes are always
atomically updated to their old values.  This works, but results in
false-positive KCSAN failures because as far as KCSAN knows, this
cmpxchg() operation is updating all four bytes.

This commit therefore encloses the cmpxchg() in a data_race() and adds
a single-byte instrument_atomic_read_write(), thus telling KCSAN exactly
what is going on so as to avoid the false positives.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Cc: Marco Elver <elver@google.com>
Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>

...

This commit is contained in:

Paul E. McKenney 2024-03-08 13:26:26 -08:00 • committed by Uladzislau Rezki (Sony)

parent ae2b217ab5

commit fc2897d2ab

1 changed files with 9 additions and 1 deletions

Show all changes Ignore whitespace when comparing lines Ignore changes in amount of whitespace Ignore changes in whitespace at EOL

Download patch file Download diff file Expand all files Collapse all files

10

kernel/rcu/tasks.h

View file