rcu/context_tracking: Merge dynticks counter and context tracking states
Updating the context tracking state and the RCU dynticks counter
atomically in a single operation is a first step towards improving CPU
isolation. This makes the context tracking state updates fully ordered
and therefore allow for later enhancements such as postponing some work
while a task is running isolated in userspace until it ever comes back
to the kernel.
The state field becomes divided in two parts:
1) Two Lower bits for context tracking state:
CONTEXT_KERNEL = 0
CONTEXT_IDLE = 1,
CONTEXT_USER = 2,
CONTEXT_GUEST = 3,
2) Higher bits for RCU eqs dynticks counting:
RCU_DYNTICKS_IDX = 4
The dynticks counting is always incremented by this value.
(state & RCU_DYNTICKS_IDX) means we are NOT in an extended quiescent
state. This makes the chance for a collision more likely between two
RCU dynticks snapshots but wrapping up 28 bits of eqs dynticks
increments still takes some bad luck (also rdp.dynticks_snap could be
converted from int to long?)
Some RCU eqs functions have been renamed to better reflect their broader
scope that now include context tracking state.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Cc: Paul E. McKenney <paulmck@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Neeraj Upadhyay <quic_neeraju@quicinc.com>
Cc: Uladzislau Rezki <uladzislau.rezki@sony.com>
Cc: Joel Fernandes <joel@joelfernandes.org>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Nicolas Saenz Julienne <nsaenz@kernel.org>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Xiongfeng Wang <wangxiongfeng2@huawei.com>
Cc: Yu Liao<liaoyu15@huawei.com>
Cc: Phil Auld <pauld@redhat.com>
Cc: Paul Gortmaker<paul.gortmaker@windriver.com>
Cc: Alex Belits <abelits@marvell.com>
5 files changed
