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authorOleg Nesterov <oleg@redhat.com>2010-03-15 10:10:03 +0100
committerThomas Gleixner <tglx@linutronix.de>2010-07-20 12:25:53 +0200
commita1e0f4a378e0d6d2f03c59c9699bb7746938c520 (patch)
treedb02363fa23aaa13c4212d865207b58539353a18 /include
parentdd56c23f5622da2407c764970be1e37ac122c378 (diff)
downloadlwn-a1e0f4a378e0d6d2f03c59c9699bb7746938c520.tar.gz
lwn-a1e0f4a378e0d6d2f03c59c9699bb7746938c520.zip
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. [ upstream: 897f0b3c3ff40b443c84e271bef19bd6ae885195 ] 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')
-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? */
extern int cpuset_init(void);
extern void cpuset_init_smp(void);
extern void cpuset_cpus_allowed(struct task_struct *p, struct cpumask *mask);
-extern void cpuset_cpus_allowed_locked(struct task_struct *p,
- struct cpumask *mask);
extern nodemask_t cpuset_mems_allowed(struct task_struct *p);
#define cpuset_current_mems_allowed (current->mems_allowed)
void cpuset_init_current_mems_allowed(void);
@@ -69,9 +67,6 @@ struct seq_file;
extern void cpuset_task_status_allowed(struct seq_file *m,
struct task_struct *task);
-extern void cpuset_lock(void);
-extern void cpuset_unlock(void);
-
extern int cpuset_mem_spread_node(void);
static inline int cpuset_do_page_mem_spread(void)
@@ -105,11 +100,6 @@ static inline void cpuset_cpus_allowed(struct task_struct *p,
{
cpumask_copy(mask, cpu_possible_mask);
}
-static inline void cpuset_cpus_allowed_locked(struct task_struct *p,
- struct cpumask *mask)
-{
- cpumask_copy(mask, cpu_possible_mask);
-}
static inline nodemask_t cpuset_mems_allowed(struct task_struct *p)
{
@@ -157,9 +147,6 @@ static inline void cpuset_task_status_allowed(struct seq_file *m,
{
}
-static inline void cpuset_lock(void) {}
-static inline void cpuset_unlock(void) {}
-
static inline int cpuset_mem_spread_node(void)
{
return 0;