diff options
Diffstat (limited to 'debian/patches-rt/0159-rcu-Make-ksoftirqd-do-RCU-quiescent-states.patch')
| -rw-r--r-- | debian/patches-rt/0159-rcu-Make-ksoftirqd-do-RCU-quiescent-states.patch | 117 |
1 files changed, 117 insertions, 0 deletions
diff --git a/debian/patches-rt/0159-rcu-Make-ksoftirqd-do-RCU-quiescent-states.patch b/debian/patches-rt/0159-rcu-Make-ksoftirqd-do-RCU-quiescent-states.patch new file mode 100644 index 000000000..44b6d052a --- /dev/null +++ b/debian/patches-rt/0159-rcu-Make-ksoftirqd-do-RCU-quiescent-states.patch @@ -0,0 +1,117 @@ +From 19f2644a64bbf80c134cc923b59d5448d76af806 Mon Sep 17 00:00:00 2001 +From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> +Date: Wed, 5 Oct 2011 11:45:18 -0700 +Subject: [PATCH 159/347] rcu: Make ksoftirqd do RCU quiescent states +Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.19/older/patches-4.19.246-rt110.tar.xz + +Implementing RCU-bh in terms of RCU-preempt makes the system vulnerable +to network-based denial-of-service attacks. This patch therefore +makes __do_softirq() invoke rcu_bh_qs(), but only when __do_softirq() +is running in ksoftirqd context. A wrapper layer in interposed so that +other calls to __do_softirq() avoid invoking rcu_bh_qs(). The underlying +function __do_softirq_common() does the actual work. + +The reason that rcu_bh_qs() is bad in these non-ksoftirqd contexts is +that there might be a local_bh_enable() inside an RCU-preempt read-side +critical section. This local_bh_enable() can invoke __do_softirq() +directly, so if __do_softirq() were to invoke rcu_bh_qs() (which just +calls rcu_preempt_qs() in the PREEMPT_RT_FULL case), there would be +an illegal RCU-preempt quiescent state in the middle of an RCU-preempt +read-side critical section. Therefore, quiescent states can only happen +in cases where __do_softirq() is invoked directly from ksoftirqd. + +Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> +Link: http://lkml.kernel.org/r/20111005184518.GA21601@linux.vnet.ibm.com +Signed-off-by: Thomas Gleixner <tglx@linutronix.de> +--- + kernel/rcu/tree.c | 18 +++++++++++++----- + kernel/rcu/tree_plugin.h | 8 +++++++- + 2 files changed, 20 insertions(+), 6 deletions(-) + +diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c +index 1456a3d97971..1a40e3d44cb8 100644 +--- a/kernel/rcu/tree.c ++++ b/kernel/rcu/tree.c +@@ -244,7 +244,19 @@ void rcu_sched_qs(void) + this_cpu_ptr(&rcu_sched_data), true); + } + +-#ifndef CONFIG_PREEMPT_RT_FULL ++#ifdef CONFIG_PREEMPT_RT_FULL ++static void rcu_preempt_qs(void); ++ ++void rcu_bh_qs(void) ++{ ++ unsigned long flags; ++ ++ /* Callers to this function, rcu_preempt_qs(), must disable irqs. */ ++ local_irq_save(flags); ++ rcu_preempt_qs(); ++ local_irq_restore(flags); ++} ++#else + void rcu_bh_qs(void) + { + RCU_LOCKDEP_WARN(preemptible(), "rcu_bh_qs() invoked with preemption enabled!!!"); +@@ -255,10 +267,6 @@ void rcu_bh_qs(void) + __this_cpu_write(rcu_bh_data.cpu_no_qs.b.norm, false); + } + } +-#else +-void rcu_bh_qs(void) +-{ +-} + #endif + + /* +diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h +index e9ce51e19e87..938e64c69d18 100644 +--- a/kernel/rcu/tree_plugin.h ++++ b/kernel/rcu/tree_plugin.h +@@ -29,6 +29,7 @@ + #include <linux/oom.h> + #include <linux/sched/debug.h> + #include <linux/smpboot.h> ++#include <linux/jiffies.h> + #include <linux/sched/isolation.h> + #include <uapi/linux/sched/types.h> + #include "../time/tick-internal.h" +@@ -1408,7 +1409,7 @@ static void rcu_prepare_kthreads(int cpu) + + #endif /* #else #ifdef CONFIG_RCU_BOOST */ + +-#if !defined(CONFIG_RCU_FAST_NO_HZ) ++#if !defined(CONFIG_RCU_FAST_NO_HZ) || defined(CONFIG_PREEMPT_RT_FULL) + + /* + * Check to see if any future RCU-related work will need to be done +@@ -1424,7 +1425,9 @@ int rcu_needs_cpu(u64 basemono, u64 *nextevt) + *nextevt = KTIME_MAX; + return rcu_cpu_has_callbacks(NULL); + } ++#endif /* !defined(CONFIG_RCU_FAST_NO_HZ) || defined(CONFIG_PREEMPT_RT_FULL) */ + ++#if !defined(CONFIG_RCU_FAST_NO_HZ) + /* + * Because we do not have RCU_FAST_NO_HZ, don't bother cleaning up + * after it. +@@ -1521,6 +1524,8 @@ static bool __maybe_unused rcu_try_advance_all_cbs(void) + return cbs_ready; + } + ++#ifndef CONFIG_PREEMPT_RT_FULL ++ + /* + * Allow the CPU to enter dyntick-idle mode unless it has callbacks ready + * to invoke. If the CPU has callbacks, try to advance them. Tell the +@@ -1563,6 +1568,7 @@ int rcu_needs_cpu(u64 basemono, u64 *nextevt) + *nextevt = basemono + dj * TICK_NSEC; + return 0; + } ++#endif /* #ifndef CONFIG_PREEMPT_RT_FULL */ + + /* + * Prepare a CPU for idle from an RCU perspective. The first major task +-- +2.36.1 + |