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| -rw-r--r-- | Documentation/RCU/Design/Requirements/Requirements.rst | 12 |
1 files changed, 6 insertions, 6 deletions
diff --git a/Documentation/RCU/Design/Requirements/Requirements.rst b/Documentation/RCU/Design/Requirements/Requirements.rst index ba417a08b93d..b5cdbba3ec2e 100644 --- a/Documentation/RCU/Design/Requirements/Requirements.rst +++ b/Documentation/RCU/Design/Requirements/Requirements.rst @@ -2780,12 +2780,12 @@ 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(), |