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

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This reverts commit 616c310e83.
(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.

Reported-by: Sasha Levin <levinsasha928@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Tested-by: Sasha Levin <levinsasha928@gmail.com>
This commit is contained in:
Paul E. McKenney 2012-07-02 07:08:42 -07:00
commit cba6d0d64e
8 changed files with 19 additions and 16 deletions
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1
include/linux/rcupdate.h
View file

@ -184,7 +184,6 @@ static inline int rcu_preempt_depth(void)
/* Internal to kernel */
extern void rcu_sched_qs(int cpu);
extern void rcu_bh_qs(int cpu);
extern void rcu_preempt_note_context_switch(void);
extern void rcu_check_callbacks(int cpu, int user);
struct notifier_block;
extern void rcu_idle_enter(void);

6
include/linux/rcutiny.h
View file

@ -87,6 +87,10 @@ static inline void kfree_call_rcu(struct rcu_head *head,
#ifdef CONFIG_TINY_RCU
static inline void rcu_preempt_note_context_switch(void)
{
}
static inline int rcu_needs_cpu(int cpu, unsigned long *delta_jiffies)
{
*delta_jiffies = ULONG_MAX;
@ -95,6 +99,7 @@ static inline int rcu_needs_cpu(int cpu, unsigned long *delta_jiffies)
#else /* #ifdef CONFIG_TINY_RCU */
void rcu_preempt_note_context_switch(void);
int rcu_preempt_needs_cpu(void);
static 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)
static inline void rcu_note_context_switch(int cpu)
{
rcu_sched_qs(cpu);
rcu_preempt_note_context_switch();
}
/*

10
include/linux/sched.h
View file

@ -1871,22 +1871,12 @@ static inline void rcu_copy_process(struct task_struct *p)
INIT_LIST_HEAD(&p->rcu_node_entry);
}
static inline void rcu_switch_from(struct task_struct *prev)
{
if (prev->rcu_read_lock_nesting != 0)
rcu_preempt_note_context_switch();
}
#else
static inline void rcu_copy_process(struct task_struct *p)
{
}
static inline void rcu_switch_from(struct task_struct *prev)
{
}
#endif
#ifdef CONFIG_SMP