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authorOleg Nesterov <oleg@redhat.com>2010-03-15 05:10:03 -0400
committerIngo Molnar <mingo@elte.hu>2010-04-02 14:12:01 -0400
commit897f0b3c3ff40b443c84e271bef19bd6ae885195 (patch)
tree6b969149bb59591a1c9485de405639db6c4208d6 /include/linux/cpuset.h
parent25c2d55c00c6097e6792ebf21e31342f23b9b768 (diff)
sched: Kill the broken and deadlockable cpuset_lock/cpuset_cpus_allowed_locked code
This patch just states the fact the cpusets/cpuhotplug interaction is broken and removes the deadlockable code which only pretends to work. - cpuset_lock() doesn't really work. It is needed for cpuset_cpus_allowed_locked() but we can't take this lock in try_to_wake_up()->select_fallback_rq() path. - cpuset_lock() is deadlockable. Suppose that a task T bound to CPU takes callback_mutex. If cpu_down(CPU) happens before T drops callback_mutex stop_machine() preempts T, then migration_call(CPU_DEAD) tries to take cpuset_lock() and hangs forever because CPU is already dead and thus T can't be scheduled. - cpuset_cpus_allowed_locked() is deadlockable too. It takes task_lock() which is not irq-safe, but try_to_wake_up() can be called from irq. Kill them, and change select_fallback_rq() to use cpu_possible_mask, like we currently do without CONFIG_CPUSETS. Also, with or without this patch, with or without CONFIG_CPUSETS, the callers of select_fallback_rq() can race with each other or with set_cpus_allowed() pathes. The subsequent patches try to to fix these problems. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <20100315091003.GA9123@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'include/linux/cpuset.h')
-rw-r--r--include/linux/cpuset.h13
1 files changed, 0 insertions, 13 deletions
diff --git a/include/linux/cpuset.h b/include/linux/cpuset.h
index a5740fc4d04b..eeaaee746bee 100644
--- a/include/linux/cpuset.h
+++ b/include/linux/cpuset.h
@@ -21,8 +21,6 @@ extern int number_of_cpusets; /* How many cpusets are defined in system? */
21extern int cpuset_init(void); 21extern int cpuset_init(void);
22extern void cpuset_init_smp(void); 22extern void cpuset_init_smp(void);
23extern void cpuset_cpus_allowed(struct task_struct *p, struct cpumask *mask); 23extern void cpuset_cpus_allowed(struct task_struct *p, struct cpumask *mask);
24extern void cpuset_cpus_allowed_locked(struct task_struct *p,
25 struct cpumask *mask);
26extern nodemask_t cpuset_mems_allowed(struct task_struct *p); 24extern nodemask_t cpuset_mems_allowed(struct task_struct *p);
27#define cpuset_current_mems_allowed (current->mems_allowed) 25#define cpuset_current_mems_allowed (current->mems_allowed)
28void cpuset_init_current_mems_allowed(void); 26void cpuset_init_current_mems_allowed(void);
@@ -69,9 +67,6 @@ struct seq_file;
69extern void cpuset_task_status_allowed(struct seq_file *m, 67extern void cpuset_task_status_allowed(struct seq_file *m,
70 struct task_struct *task); 68 struct task_struct *task);
71 69
72extern void cpuset_lock(void);
73extern void cpuset_unlock(void);
74
75extern int cpuset_mem_spread_node(void); 70extern int cpuset_mem_spread_node(void);
76 71
77static inline int cpuset_do_page_mem_spread(void) 72static inline int cpuset_do_page_mem_spread(void)
@@ -105,11 +100,6 @@ static inline void cpuset_cpus_allowed(struct task_struct *p,
105{ 100{
106 cpumask_copy(mask, cpu_possible_mask); 101 cpumask_copy(mask, cpu_possible_mask);
107} 102}
108static inline void cpuset_cpus_allowed_locked(struct task_struct *p,
109 struct cpumask *mask)
110{
111 cpumask_copy(mask, cpu_possible_mask);
112}
113 103
114static inline nodemask_t cpuset_mems_allowed(struct task_struct *p) 104static inline nodemask_t cpuset_mems_allowed(struct task_struct *p)
115{ 105{
@@ -157,9 +147,6 @@ static inline void cpuset_task_status_allowed(struct seq_file *m,
157{ 147{
158} 148}
159 149
160static inline void cpuset_lock(void) {}
161static inline void cpuset_unlock(void) {}
162
163static inline int cpuset_mem_spread_node(void) 150static inline int cpuset_mem_spread_node(void)
164{ 151{
165 return 0; 152 return 0;