Messages in this thread Patch in this message | | | Date | Thu, 12 May 2005 00:46:54 +0530 | From | Dinakar Guniguntala <> | Subject | [PATCH] cpusets+hotplug+preepmt broken |
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cpusets+hotplug+preempt hangs up the machine, if both cpuset and hotplug operations are going on simultaneously
I also get this oops first
scheduling while atomic: cpuoff.sh/0x00000001/25331 [<c040195d>] schedule+0xa4d/0xa60 [<c0401b25>] wait_for_completion+0xc5/0xf0 [<c011a200>] default_wake_function+0x0/0x20 [<c0400cd3>] __down+0x83/0x110 [<c011a200>] default_wake_function+0x0/0x20 [<c0400eab>] __down_failed+0x7/0xc [<c0141fe7>] .text.lock.cpuset+0x105/0x15e [<c011b860>] move_task_off_dead_cpu+0x130/0x1f0 [<c011ba7c>] migrate_live_tasks+0x8c/0x90 [<c011be25>] migration_call+0x75/0x2c0 [<c01423f2>] __stop_machine_run+0x92/0xb0 [<c012e0dd>] notifier_call_chain+0x2d/0x50 [<c013a6fb>] cpu_down+0x16b/0x2a0 [<c027ddfb>] store_online+0x5b/0x80 [<c027ae15>] sysdev_store+0x35/0x40 [<c019f43e>] flush_write_buffer+0x3e/0x50 [<c019f4a8>] sysfs_write_file+0x58/0x80 [<c0163d26>] vfs_write+0xc6/0x180 [<c0163eb1>] sys_write+0x51/0x80 [<c01034e5>] syscall_call+0x7/0xb
It looks like hotplug operations need to take cpuset_sem as well.
Here is a patch against 2.6.12-rc2-mm3. Should apply against rc3-mm3 as well This has been tested and seems to fix the problem
-Dinakar Signed-off-by: Dinakar Guniguntala <dino@in.ibm.com>
diff -Naurp linux-2.6.12-rc2-mm3.orig/include/linux/cpuset.h linux-2.6.12-rc2-mm3-0/include/linux/cpuset.h --- linux-2.6.12-rc2-mm3.orig/include/linux/cpuset.h 2005-05-11 19:44:42.000000000 +0530 +++ linux-2.6.12-rc2-mm3-0/include/linux/cpuset.h 2005-05-11 19:51:31.000000000 +0530 @@ -14,6 +14,10 @@ #ifdef CONFIG_CPUSETS +extern struct semaphore cpuset_sem; +#define lock_cpuset_sem() down(&cpuset_sem); +#define unlock_cpuset_sem() up(&cpuset_sem); + extern int cpuset_init(void); extern void cpuset_init_smp(void); extern void cpuset_fork(struct task_struct *p); @@ -29,6 +33,9 @@ extern char *cpuset_task_status_allowed( #else /* !CONFIG_CPUSETS */ +#define lock_cpuset_sem() do { } while (0) +#define unlock_cpuset_sem() do { } while (0) + static inline int cpuset_init(void) { return 0; } static inline void cpuset_init_smp(void) {} static inline void cpuset_fork(struct task_struct *p) {} diff -Naurp linux-2.6.12-rc2-mm3.orig/kernel/cpu.c linux-2.6.12-rc2-mm3-0/kernel/cpu.c --- linux-2.6.12-rc2-mm3.orig/kernel/cpu.c 2005-05-11 19:44:42.000000000 +0530 +++ linux-2.6.12-rc2-mm3-0/kernel/cpu.c 2005-05-11 19:46:38.000000000 +0530 @@ -10,6 +10,7 @@ #include <linux/sched.h> #include <linux/unistd.h> #include <linux/cpu.h> +#include <linux/cpuset.h> #include <linux/module.h> #include <linux/kthread.h> #include <linux/stop_machine.h> @@ -82,6 +83,7 @@ int cpu_down(unsigned int cpu) if ((err = lock_cpu_hotplug_interruptible()) != 0) return err; + lock_cpuset_sem(); if (num_online_cpus() == 1) { err = -EBUSY; @@ -145,6 +147,7 @@ out_thread: out_allowed: set_cpus_allowed(current, old_allowed); out: + unlock_cpuset_sem(); unlock_cpu_hotplug(); return err; } @@ -157,6 +160,7 @@ int __devinit cpu_up(unsigned int cpu) if ((ret = down_interruptible(&cpucontrol)) != 0) return ret; + lock_cpuset_sem(); if (cpu_online(cpu) || !cpu_present(cpu)) { ret = -EINVAL; @@ -184,6 +188,7 @@ out_notify: if (ret != 0) notifier_call_chain(&cpu_chain, CPU_UP_CANCELED, hcpu); out: + unlock_cpuset_sem(); up(&cpucontrol); return ret; } diff -Naurp linux-2.6.12-rc2-mm3.orig/kernel/cpuset.c linux-2.6.12-rc2-mm3-0/kernel/cpuset.c --- linux-2.6.12-rc2-mm3.orig/kernel/cpuset.c 2005-05-11 19:44:42.000000000 +0530 +++ linux-2.6.12-rc2-mm3-0/kernel/cpuset.c 2005-05-11 19:55:08.000000000 +0530 @@ -180,7 +180,7 @@ static struct super_block *cpuset_sb = N * for any special hack to ensure that top_cpuset cannot be deleted. */ -static DECLARE_MUTEX(cpuset_sem); +DECLARE_MUTEX(cpuset_sem); /* * A couple of forward declarations required, due to cyclic reference loop: @@ -1430,17 +1430,17 @@ void cpuset_exit(struct task_struct *tsk * attached to the specified @tsk. Guaranteed to return some non-empty * subset of cpu_online_map, even if this means going outside the * tasks cpuset. + * + * Call with cpuset_sem held. **/ cpumask_t cpuset_cpus_allowed(const struct task_struct *tsk) { cpumask_t mask; - down(&cpuset_sem); task_lock((struct task_struct *)tsk); guarantee_online_cpus(tsk->cpuset, &mask); task_unlock((struct task_struct *)tsk); - up(&cpuset_sem); return mask; } diff -Naurp linux-2.6.12-rc2-mm3.orig/kernel/sched.c linux-2.6.12-rc2-mm3-0/kernel/sched.c --- linux-2.6.12-rc2-mm3.orig/kernel/sched.c 2005-05-11 19:44:42.000000000 +0530 +++ linux-2.6.12-rc2-mm3-0/kernel/sched.c 2005-05-11 19:48:29.000000000 +0530 @@ -3608,11 +3608,13 @@ long sched_setaffinity(pid_t pid, cpumas cpumask_t cpus_allowed; lock_cpu_hotplug(); + lock_cpuset_sem(); read_lock(&tasklist_lock); p = find_process_by_pid(pid); if (!p) { read_unlock(&tasklist_lock); + unlock_cpuset_sem(); unlock_cpu_hotplug(); return -ESRCH; } @@ -3636,6 +3638,7 @@ long sched_setaffinity(pid_t pid, cpumas out_unlock: put_task_struct(p); + unlock_cpuset_sem(); unlock_cpu_hotplug(); return retval; }
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