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Diffstat (limited to '')
| -rw-r--r-- | debian/patches-rt/0155-sched-migrate_disable-fallback-to-preempt_disable-in.patch | 204 |
1 files changed, 204 insertions, 0 deletions
diff --git a/debian/patches-rt/0155-sched-migrate_disable-fallback-to-preempt_disable-in.patch b/debian/patches-rt/0155-sched-migrate_disable-fallback-to-preempt_disable-in.patch new file mode 100644 index 000000000..c471ea20d --- /dev/null +++ b/debian/patches-rt/0155-sched-migrate_disable-fallback-to-preempt_disable-in.patch @@ -0,0 +1,204 @@ +From e85e95b0e59b7d493402419e3a63a06978a06452 Mon Sep 17 00:00:00 2001 +From: Sebastian Andrzej Siewior <bigeasy@linutronix.de> +Date: Thu, 5 Jul 2018 14:44:51 +0200 +Subject: [PATCH 155/347] sched/migrate_disable: fallback to preempt_disable() + instead barrier() +Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.19/older/patches-4.19.246-rt110.tar.xz + +On SMP + !RT migrate_disable() is still around. It is not part of spin_lock() +anymore so it has almost no users. However the futex code has a workaround for +the !in_atomic() part of migrate disable which fails because the matching +migrade_disable() is no longer part of spin_lock(). + +On !SMP + !RT migrate_disable() is reduced to barrier(). This is not optimal +because we few spots where a "preempt_disable()" statement was replaced with +"migrate_disable()". + +We also used the migration_disable counter to figure out if a sleeping lock is +acquired so RCU does not complain about schedule() during rcu_read_lock() while +a sleeping lock is held. This changed, we no longer use it, we have now a +sleeping_lock counter for the RCU purpose. + +This means we can now: +- for SMP + RT_BASE + full migration program, nothing changes here + +- for !SMP + RT_BASE + the migration counting is no longer required. It used to ensure that the task + is not migrated to another CPU and that this CPU remains online. !SMP ensures + that already. + Move it to CONFIG_SCHED_DEBUG so the counting is done for debugging purpose + only. + +- for all other cases including !RT + fallback to preempt_disable(). The only remaining users of migrate_disable() + are those which were converted from preempt_disable() and the futex + workaround which is already in the preempt_disable() section due to the + spin_lock that is held. + +Cc: stable-rt@vger.kernel.org +Reported-by: joe.korty@concurrent-rt.com +Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> +--- + include/linux/preempt.h | 6 +++--- + include/linux/sched.h | 4 ++-- + kernel/sched/core.c | 23 +++++++++++------------ + kernel/sched/debug.c | 2 +- + 4 files changed, 17 insertions(+), 18 deletions(-) + +diff --git a/include/linux/preempt.h b/include/linux/preempt.h +index 9eafc34898b4..ed8413e7140f 100644 +--- a/include/linux/preempt.h ++++ b/include/linux/preempt.h +@@ -204,7 +204,7 @@ do { \ + + #define preemptible() (preempt_count() == 0 && !irqs_disabled()) + +-#ifdef CONFIG_SMP ++#if defined(CONFIG_SMP) && defined(CONFIG_PREEMPT_RT_BASE) + + extern void migrate_disable(void); + extern void migrate_enable(void); +@@ -221,8 +221,8 @@ static inline int __migrate_disabled(struct task_struct *p) + } + + #else +-#define migrate_disable() barrier() +-#define migrate_enable() barrier() ++#define migrate_disable() preempt_disable() ++#define migrate_enable() preempt_enable() + static inline int __migrate_disabled(struct task_struct *p) + { + return 0; +diff --git a/include/linux/sched.h b/include/linux/sched.h +index 4f8fcba23c1d..ceb3bdfb6bc4 100644 +--- a/include/linux/sched.h ++++ b/include/linux/sched.h +@@ -667,7 +667,7 @@ struct task_struct { + int nr_cpus_allowed; + const cpumask_t *cpus_ptr; + cpumask_t cpus_mask; +-#if defined(CONFIG_PREEMPT_COUNT) && defined(CONFIG_SMP) ++#if defined(CONFIG_SMP) && defined(CONFIG_PREEMPT_RT_BASE) + int migrate_disable; + int migrate_disable_update; + # ifdef CONFIG_SCHED_DEBUG +@@ -675,8 +675,8 @@ struct task_struct { + # endif + + #elif !defined(CONFIG_SMP) && defined(CONFIG_PREEMPT_RT_BASE) +- int migrate_disable; + # ifdef CONFIG_SCHED_DEBUG ++ int migrate_disable; + int migrate_disable_atomic; + # endif + #endif +diff --git a/kernel/sched/core.c b/kernel/sched/core.c +index 555dea10764e..0c44c16244a1 100644 +--- a/kernel/sched/core.c ++++ b/kernel/sched/core.c +@@ -1031,7 +1031,7 @@ void set_cpus_allowed_common(struct task_struct *p, const struct cpumask *new_ma + p->nr_cpus_allowed = cpumask_weight(new_mask); + } + +-#if defined(CONFIG_PREEMPT_COUNT) && defined(CONFIG_SMP) ++#if defined(CONFIG_SMP) && defined(CONFIG_PREEMPT_RT_BASE) + int __migrate_disabled(struct task_struct *p) + { + return p->migrate_disable; +@@ -1071,7 +1071,7 @@ static void __do_set_cpus_allowed_tail(struct task_struct *p, + + void do_set_cpus_allowed(struct task_struct *p, const struct cpumask *new_mask) + { +-#if defined(CONFIG_PREEMPT_COUNT) && defined(CONFIG_SMP) ++#if defined(CONFIG_SMP) && defined(CONFIG_PREEMPT_RT_BASE) + if (__migrate_disabled(p)) { + lockdep_assert_held(&p->pi_lock); + +@@ -1145,7 +1145,7 @@ static int __set_cpus_allowed_ptr(struct task_struct *p, + if (cpumask_test_cpu(task_cpu(p), new_mask) || __migrate_disabled(p)) + goto out; + +-#if defined(CONFIG_PREEMPT_COUNT) && defined(CONFIG_SMP) ++#if defined(CONFIG_SMP) && defined(CONFIG_PREEMPT_RT_BASE) + if (__migrate_disabled(p)) { + p->migrate_disable_update = 1; + goto out; +@@ -7204,7 +7204,7 @@ const u32 sched_prio_to_wmult[40] = { + + #undef CREATE_TRACE_POINTS + +-#if defined(CONFIG_PREEMPT_COUNT) && defined(CONFIG_SMP) ++#if defined(CONFIG_SMP) && defined(CONFIG_PREEMPT_RT_BASE) + + static inline void + update_nr_migratory(struct task_struct *p, long delta) +@@ -7352,45 +7352,44 @@ EXPORT_SYMBOL(migrate_enable); + #elif !defined(CONFIG_SMP) && defined(CONFIG_PREEMPT_RT_BASE) + void migrate_disable(void) + { ++#ifdef CONFIG_SCHED_DEBUG + struct task_struct *p = current; + + if (in_atomic() || irqs_disabled()) { +-#ifdef CONFIG_SCHED_DEBUG + p->migrate_disable_atomic++; +-#endif + return; + } +-#ifdef CONFIG_SCHED_DEBUG ++ + if (unlikely(p->migrate_disable_atomic)) { + tracing_off(); + WARN_ON_ONCE(1); + } +-#endif + + p->migrate_disable++; ++#endif ++ barrier(); + } + EXPORT_SYMBOL(migrate_disable); + + void migrate_enable(void) + { ++#ifdef CONFIG_SCHED_DEBUG + struct task_struct *p = current; + + if (in_atomic() || irqs_disabled()) { +-#ifdef CONFIG_SCHED_DEBUG + p->migrate_disable_atomic--; +-#endif + return; + } + +-#ifdef CONFIG_SCHED_DEBUG + if (unlikely(p->migrate_disable_atomic)) { + tracing_off(); + WARN_ON_ONCE(1); + } +-#endif + + WARN_ON_ONCE(p->migrate_disable <= 0); + p->migrate_disable--; ++#endif ++ barrier(); + } + EXPORT_SYMBOL(migrate_enable); + #endif +diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c +index dc3f3e6fa0bd..169b98c12da7 100644 +--- a/kernel/sched/debug.c ++++ b/kernel/sched/debug.c +@@ -988,7 +988,7 @@ void proc_sched_show_task(struct task_struct *p, struct pid_namespace *ns, + P(dl.runtime); + P(dl.deadline); + } +-#if defined(CONFIG_PREEMPT_COUNT) && defined(CONFIG_SMP) ++#if defined(CONFIG_SMP) && defined(CONFIG_PREEMPT_RT_BASE) + P(migrate_disable); + #endif + P(nr_cpus_allowed); +-- +2.36.1 + |