| Message ID | 20220616135347.1351441-1-qiang1.zhang@intel.com (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | cb58562318cf1fa7ad7c2c4c8d8e847c7942df66 |
| Headers | show |
| Series | rcu: Fix rcu_read_unlock_strict() strict QS reporting | expand |
On Thu, Jun 16, 2022 at 09:53:47PM +0800, Zqiang wrote: > When running a kerenl with CONFIG_PREEMPT=n and > CONFIG_RCU_STRICT_GRACE_PERIOD=y, the QS state will be reported > directly after exiting the last level of RCU critical section and > in non irqs-disable context, but maybe the CPU's rcu_data > structure's ->cpu_no_qs.b.norm is not cleared, as a result the > rcu_report_qs_rdp() will exit early, and not report QS state. > > This commit will clear CPU's rcu_data structure's ->cpu_no_qs.b.norm > before invoke rcu_report_qs_rdp(). > > Signed-off-by: Zqiang <qiang1.zhang@intel.com> Good point, thank you! Queued for review and testing with the usual wordsmithing shown below. As always, please check. Thanx, Paul ------------------------------------------------------------------------ commit cb58562318cf1fa7ad7c2c4c8d8e847c7942df66 Author: Zqiang <qiang1.zhang@intel.com> Date: Thu Jun 16 21:53:47 2022 +0800 rcu: Fix rcu_read_unlock_strict() strict QS reporting Kernels built with CONFIG_PREEMPT=n and CONFIG_RCU_STRICT_GRACE_PERIOD=y report the quiescent state directly from the outermost rcu_read_unlock(). However, the current CPU's rcu_data structure's ->cpu_no_qs.b.norm might still be set, in which case rcu_report_qs_rdp() will exit early, thus failing to report quiescent state. This commit therefore causes rcu_read_unlock_strict() to clear CPU's rcu_data structure's ->cpu_no_qs.b.norm field before invoking rcu_report_qs_rdp(). Signed-off-by: Zqiang <qiang1.zhang@intel.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index b2c01919b92c0..dc78726b993fd 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -824,6 +824,7 @@ void rcu_read_unlock_strict(void) if (irqs_disabled() || preempt_count() || !rcu_state.gp_kthread) return; rdp = this_cpu_ptr(&rcu_data); + rdp->cpu_no_qs.b.norm = false; rcu_report_qs_rdp(rdp); udelay(rcu_unlock_delay); }
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index b2c01919b92c..dc78726b993f 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -824,6 +824,7 @@ void rcu_read_unlock_strict(void) if (irqs_disabled() || preempt_count() || !rcu_state.gp_kthread) return; rdp = this_cpu_ptr(&rcu_data); + rdp->cpu_no_qs.b.norm = false; rcu_report_qs_rdp(rdp); udelay(rcu_unlock_delay); }
When running a kerenl with CONFIG_PREEMPT=n and CONFIG_RCU_STRICT_GRACE_PERIOD=y, the QS state will be reported directly after exiting the last level of RCU critical section and in non irqs-disable context, but maybe the CPU's rcu_data structure's ->cpu_no_qs.b.norm is not cleared, as a result the rcu_report_qs_rdp() will exit early, and not report QS state. This commit will clear CPU's rcu_data structure's ->cpu_no_qs.b.norm before invoke rcu_report_qs_rdp(). Signed-off-by: Zqiang <qiang1.zhang@intel.com> --- kernel/rcu/tree_plugin.h | 1 + 1 file changed, 1 insertion(+)