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Revert "rcu: Move PREEMPT_RCU preemption to switch_to() invocation"

This reverts commit 616c310e83b872024271c915c1b9ab505b9efad9. (Move PREEMPT_RCU preemption to switch_to() invocation). Testing by Sasha Levin <levinsasha928@gmail.com> showed that this can result in deadlock due to invoking the scheduler when one of the runqueue locks is held. Because this commit was simply a performance optimization, revert it.

Paul E. McKenney committed 14 years ago

Commit cba6d0d1 parent 6887a418 files · +19 −16Browse files

Unified · Split

8 files
  1. arch/um/drivers/mconsole_kern.c +0 −1
  2. include/linux/rcupdate.h +0 −1
  3. include/linux/rcutiny.h +6 −0
  4. include/linux/sched.h +0 −10
  5. kernel/rcutree.c +1 −0
  6. kernel/rcutree.h +1 −0
  7. kernel/rcutree_plugin.h +11 −3
  8. kernel/sched/core.c +0 −1
arch/um/drivers/mconsole_kern.c+0−1
@@ -705,7 +705,6 @@ static void stack_proc(void *arg) · 704 unmodified lines
705 struct task_struct *from = current, *to = arg;705 struct task_struct *from = current, *to = arg;
706 706
707 to->thread.saved_task = from;707 to->thread.saved_task = from;
708 rcu_switch_from(from);
709 switch_to(from, to, from);708 switch_to(from, to, from);
710}709}
711 710
include/linux/rcupdate.h+0−1
@@ -184,7 +184,6 @@ static inline int rcu_preempt_depth(void) · 183 unmodified lines
184/* Internal to kernel */184/* Internal to kernel */
185extern void rcu_sched_qs(int cpu);185extern void rcu_sched_qs(int cpu);
186extern void rcu_bh_qs(int cpu);186extern void rcu_bh_qs(int cpu);
187extern void rcu_preempt_note_context_switch(void);
188extern void rcu_check_callbacks(int cpu, int user);187extern void rcu_check_callbacks(int cpu, int user);
189struct notifier_block;188struct notifier_block;
190extern void rcu_idle_enter(void);189extern void rcu_idle_enter(void);
include/linux/rcutiny.h+6−0
@@ -87,6 +87,10 @@ static inline void kfree_call_rcu(struct rcu_head *head, · 86 unmodified lines
87 87
88#ifdef CONFIG_TINY_RCU88#ifdef CONFIG_TINY_RCU
89 89
90static inline void rcu_preempt_note_context_switch(void)
91{
92}
93
90static inline int rcu_needs_cpu(int cpu, unsigned long *delta_jiffies)94static inline int rcu_needs_cpu(int cpu, unsigned long *delta_jiffies)
91{95{
92 *delta_jiffies = ULONG_MAX;96 *delta_jiffies = ULONG_MAX;
@@ -95,6 +99,7 @@ static inline int rcu_needs_cpu(int cpu, unsigned long *delta_jiffies) · 2 unmodified lines
95 99
96#else /* #ifdef CONFIG_TINY_RCU */100#else /* #ifdef CONFIG_TINY_RCU */
97 101
102void rcu_preempt_note_context_switch(void);
98int rcu_preempt_needs_cpu(void);103int rcu_preempt_needs_cpu(void);
99 104
100static inline int rcu_needs_cpu(int cpu, unsigned long *delta_jiffies)105static inline int rcu_needs_cpu(int cpu, unsigned long *delta_jiffies)
@@ -108,6 +113,7 @@ static inline int rcu_needs_cpu(int cpu, unsigned long *delta_jiffies) · 7 unmodified lines
108static inline void rcu_note_context_switch(int cpu)113static inline void rcu_note_context_switch(int cpu)
109{114{
110 rcu_sched_qs(cpu);115 rcu_sched_qs(cpu);
116 rcu_preempt_note_context_switch();
111}117}
112 118
113/*119/*
include/linux/sched.h+0−10
@@ -1871,22 +1871,12 @@ static inline void rcu_copy_process(struct task_struct *p) · 1870 unmodified lines
1871 INIT_LIST_HEAD(&p->rcu_node_entry);1871 INIT_LIST_HEAD(&p->rcu_node_entry);
1872}1872}
1873 1873
1874static inline void rcu_switch_from(struct task_struct *prev)
1875{
1876 if (prev->rcu_read_lock_nesting != 0)
1877 rcu_preempt_note_context_switch();
1878}
1879
1880#else1874#else
1881 1875
1882static inline void rcu_copy_process(struct task_struct *p)1876static inline void rcu_copy_process(struct task_struct *p)
1883{1877{
1884}1878}
1885 1879
1886static inline void rcu_switch_from(struct task_struct *prev)
1887{
1888}
1889
1890#endif1880#endif
1891 1881
1892#ifdef CONFIG_SMP1882#ifdef CONFIG_SMP
kernel/rcutree.c+1−0
@@ -201,6 +201,7 @@ void rcu_note_context_switch(int cpu) · 200 unmodified lines
201{201{
202 trace_rcu_utilization("Start context switch");202 trace_rcu_utilization("Start context switch");
203 rcu_sched_qs(cpu);203 rcu_sched_qs(cpu);
204 rcu_preempt_note_context_switch(cpu);
204 trace_rcu_utilization("End context switch");205 trace_rcu_utilization("End context switch");
205}206}
206EXPORT_SYMBOL_GPL(rcu_note_context_switch);207EXPORT_SYMBOL_GPL(rcu_note_context_switch);
kernel/rcutree.h+1−0
@@ -444,6 +444,7 @@ DECLARE_PER_CPU(char, rcu_cpu_has_work); · 443 unmodified lines
444/* Forward declarations for rcutree_plugin.h */444/* Forward declarations for rcutree_plugin.h */
445static void rcu_bootup_announce(void);445static void rcu_bootup_announce(void);
446long rcu_batches_completed(void);446long rcu_batches_completed(void);
447static void rcu_preempt_note_context_switch(int cpu);
447static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp);448static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp);
448#ifdef CONFIG_HOTPLUG_CPU449#ifdef CONFIG_HOTPLUG_CPU
449static void rcu_report_unblock_qs_rnp(struct rcu_node *rnp,450static void rcu_report_unblock_qs_rnp(struct rcu_node *rnp,
kernel/rcutree_plugin.h+11−3
@@ -153,7 +153,7 @@ static void rcu_preempt_qs(int cpu) · 152 unmodified lines
153 *153 *
154 * Caller must disable preemption.154 * Caller must disable preemption.
155 */155 */
156void rcu_preempt_note_context_switch(void)156static void rcu_preempt_note_context_switch(int cpu)
157{157{
158 struct task_struct *t = current;158 struct task_struct *t = current;
159 unsigned long flags;159 unsigned long flags;
@@ -164,7 +164,7 @@ void rcu_preempt_note_context_switch(void) · 4 unmodified lines
164 (t->rcu_read_unlock_special & RCU_READ_UNLOCK_BLOCKED) == 0) {164 (t->rcu_read_unlock_special & RCU_READ_UNLOCK_BLOCKED) == 0) {
165 165
166 /* Possibly blocking in an RCU read-side critical section. */166 /* Possibly blocking in an RCU read-side critical section. */
167 rdp = __this_cpu_ptr(rcu_preempt_state.rda);167 rdp = per_cpu_ptr(rcu_preempt_state.rda, cpu);
168 rnp = rdp->mynode;168 rnp = rdp->mynode;
169 raw_spin_lock_irqsave(&rnp->lock, flags);169 raw_spin_lock_irqsave(&rnp->lock, flags);
170 t->rcu_read_unlock_special |= RCU_READ_UNLOCK_BLOCKED;170 t->rcu_read_unlock_special |= RCU_READ_UNLOCK_BLOCKED;
@@ -228,7 +228,7 @@ void rcu_preempt_note_context_switch(void) · 57 unmodified lines
228 * means that we continue to block the current grace period.228 * means that we continue to block the current grace period.
229 */229 */
230 local_irq_save(flags);230 local_irq_save(flags);
231 rcu_preempt_qs(smp_processor_id());231 rcu_preempt_qs(cpu);
232 local_irq_restore(flags);232 local_irq_restore(flags);
233}233}
234 234
@@ -1001,6 +1001,14 @@ void rcu_force_quiescent_state(void) · 766 unmodified lines
1001}1001}
1002EXPORT_SYMBOL_GPL(rcu_force_quiescent_state);1002EXPORT_SYMBOL_GPL(rcu_force_quiescent_state);
1003 1003
1004/*
1005 * Because preemptible RCU does not exist, we never have to check for
1006 * CPUs being in quiescent states.
1007 */
1008static void rcu_preempt_note_context_switch(int cpu)
1009{
1010}
1011
1004/*1012/*
1005 * Because preemptible RCU does not exist, there are never any preempted1013 * Because preemptible RCU does not exist, there are never any preempted
1006 * RCU readers.1014 * RCU readers.
kernel/sched/core.c+0−1
@@ -2081,7 +2081,6 @@ context_switch(struct rq *rq, struct task_struct *prev, · 2080 unmodified lines
2081#endif2081#endif
2082 2082
2083 /* Here we just switch the register state and the stack. */2083 /* Here we just switch the register state and the stack. */
2084 rcu_switch_from(prev);
2085 switch_to(prev, next, prev);2084 switch_to(prev, next, prev);
2086 2085
2087 barrier();2086 barrier();