This commit updates the documentation to declare that RCU Tasks Trace is implemented as a thin wrapper around SRCU-fast.
Signed-off-by: Paul E. McKenney <paul...@kernel.org> Cc: Andrii Nakryiko <and...@kernel.org> Cc: Alexei Starovoitov <a...@kernel.org> Cc: Peter Zijlstra <pet...@infradead.org> Cc: <b...@vger.kernel.org> --- .../RCU/Design/Requirements/Requirements.rst | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) diff --git a/Documentation/RCU/Design/Requirements/Requirements.rst b/Documentation/RCU/Design/Requirements/Requirements.rst index f24b3c0b9b0dc6..4a116d7a564edc 100644 --- a/Documentation/RCU/Design/Requirements/Requirements.rst +++ b/Documentation/RCU/Design/Requirements/Requirements.rst @@ -2779,12 +2779,12 @@ Tasks Trace RCU ~~~~~~~~~~~~~~~ Some forms of tracing need to sleep in readers, but cannot tolerate -SRCU's read-side overhead, which includes a full memory barrier in both -srcu_read_lock() and srcu_read_unlock(). This need is handled by a -Tasks Trace RCU that uses scheduler locking and IPIs to synchronize with -readers. Real-time systems that cannot tolerate IPIs may build their -kernels with ``CONFIG_TASKS_TRACE_RCU_READ_MB=y``, which avoids the IPIs at -the expense of adding full memory barriers to the read-side primitives. +SRCU's read-side overhead, which includes a full memory barrier in +both srcu_read_lock() and srcu_read_unlock(). This need is handled by +a Tasks Trace RCU API implemented as thin wrappers around SRCU-fast, +which avoids the read-side memory barriers, at least for architectures +that apply noinstr to kernel entry/exit code (or that build with +``CONFIG_TASKS_TRACE_RCU_NO_MB=y``. The tasks-trace-RCU API is also reasonably compact, consisting of rcu_read_lock_trace(), rcu_read_unlock_trace(), -- 2.40.1
