Messages in this thread Patch in this message | | | Date | Mon, 10 May 2010 21:50:38 +0200 | From | Oleg Nesterov <> | Subject | [PATCH 3/4] pids: fix fork_idle() to setup ->pids correctly |
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copy_process(pid => &init_struct_pid) doesn't do attach_pid/etc.
It shouldn't, but this means that the idle threads run with the wrong pids copied from the caller's task_struct. In x86 case the caller is either kernel_init() thread or keventd.
In particular, this means that after the series of cpu_up/cpu_down an idle thread (which never exits) can run with .pid pointing to nowhere.
Change fork_idle() to initialize idle->pids[] correctly. We only set .pid = &init_struct_pid but do not add .node to list, INIT_TASK() does the same for the boot-cpu idle thread (swapper).
Signed-off-by: Oleg Nesterov <oleg@redhat.com> ---
kernel/fork.c | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-)
--- 34-rc1/kernel/fork.c~3_FORK_IDLE_SET_PIDS 2010-03-24 18:07:03.000000000 +0100 +++ 34-rc1/kernel/fork.c 2010-05-10 20:45:33.000000000 +0200 @@ -1339,6 +1339,16 @@ noinline struct pt_regs * __cpuinit __at return regs; } +static inline void init_idle_pids(struct pid_link *links) +{ + enum pid_type type; + + for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) { + INIT_HLIST_NODE(&links[type].node); /* not really needed */ + links[type].pid = &init_struct_pid; + } +} + struct task_struct * __cpuinit fork_idle(int cpu) { struct task_struct *task; @@ -1346,8 +1356,10 @@ struct task_struct * __cpuinit fork_idle task = copy_process(CLONE_VM, 0, idle_regs(®s), 0, NULL, &init_struct_pid, 0); - if (!IS_ERR(task)) + if (!IS_ERR(task)) { + init_idle_pids(task->pids); init_idle(task, cpu); + } return task; }
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