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| author |   Boqun Feng <boqun.feng@gmail.com> | 2019-10-08 13:01:40 +0800 |
|---|---|---|
| committer |   Paul E. McKenney <paulmck@kernel.org> | 2019-12-09 12:24:56 -0800 |
| commit | 9f08cf088676c12a5b53bd5a29cf04f00c787b5d (patch) | |
| tree | 41e8ee93dc186a569b07f6f0ee0472f174c1edf0 /kernel | |
| parent | rcu: Use *_ONCE() to protect lockless ->expmask accesses (diff) | |
| download | linux-dev-9f08cf088676c12a5b53bd5a29cf04f00c787b5d.tar.xz linux-dev-9f08cf088676c12a5b53bd5a29cf04f00c787b5d.zip | |
rcu: Avoid modifying mask_ofl_ipi in sync_rcu_exp_select_node_cpus()
The "mask_ofl_ipi" is used to track which CPUs get IPIed, however
in the IPI sending loop, "mask_ofl_ipi" along with another variable
"mask_ofl_test" might also get modified to record which CPUs' quiesent
states must be reported by the sync_rcu_exp_select_node_cpus() at
the end of sync_rcu_exp_select_node_cpus(). This overlap of roles
can be confusing, so this patch cleans things a little by using
"mask_ofl_ipi" solely for determining which CPUs must be IPIed and
"mask_ofl_test" for solely determining on behalf of which CPUs
sync_rcu_exp_select_node_cpus() must report a quiscent state.
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Acked-by: Marco Elver <elver@google.com>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/rcu/tree_exp.h | 13 |
1 files changed, 6 insertions, 7 deletions
diff --git a/kernel/rcu/tree_exp.h b/kernel/rcu/tree_exp.h index 69c5aa64fcfd..6a6f328a5f52 100644 --- a/kernel/rcu/tree_exp.h +++ b/kernel/rcu/tree_exp.h @@ -387,10 +387,10 @@ retry_ipi: } ret = smp_call_function_single(cpu, rcu_exp_handler, NULL, 0); put_cpu(); - if (!ret) { - mask_ofl_ipi &= ~mask; + /* The CPU will report the QS in response to the IPI. */ + if (!ret) continue; - } + /* Failed, raced with CPU hotplug operation. */ raw_spin_lock_irqsave_rcu_node(rnp, flags); if ((rnp->qsmaskinitnext & mask) && @@ -401,13 +401,12 @@ retry_ipi: schedule_timeout_uninterruptible(1); goto retry_ipi; } - /* CPU really is offline, so we can ignore it. */ - if (!(rnp->expmask & mask)) - mask_ofl_ipi &= ~mask; + /* CPU really is offline, so we must report its QS. */ + if (rnp->expmask & mask) + mask_ofl_test |= mask; raw_spin_unlock_irqrestore_rcu_node(rnp, flags); } /* Report quiescent states for those that went offline. */ - mask_ofl_test |= mask_ofl_ipi; if (mask_ofl_test) rcu_report_exp_cpu_mult(rnp, mask_ofl_test, false); } |