Messages in this thread | | | Date | Tue, 07 Mar 2006 00:06:33 +0300 | From | Oleg Nesterov <> | Subject | Re: [PATCH 01/23] tref: Implement task references. |
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I think I have a really good idea.
Forget about task ref for a moment. I thinks we can greatly simplify the pids management. We don't PIDTYPE_MAX hash tables, we need only one.
The plan:
kill PIDTYPE_TGID (copy_process/unhash_process need a simple fix)
kill 'struct pid'
Now,
struct task_struct { ... struct list_head pids[PIDTYPE_MAX]; struct list_head tgrp; ... };
static inline struct task_struct *next_thread(struct task_struct *p) { return list_entry(p->tgrp.next, struct task_struct, tgrp); }
struct pid_head { pid_t nr; struct hlist_node chain; struct list_head tasks[PIDTYPE_MAX]; };
kernel/pid.c:
static kmem_cache_t *pid_cachep;
static struct hlist_head *pid_hash; #define pid_bucket(nr) (pid_hash + pid_hashfn(nr))
// alloc_pidmap() becomes static, // do_fork() calls this instead struct pid_head *alloc_pid(void) { struct pid_head *pid;
pid = kmem_cache_alloc(pid_cachep, GFP_KERNEL);
if (likely(pid)) { enum pid_type type;
for (type = 0; type < PIDTYPE_MAX; ++type) INIT_LIST_HEAD(pid->tasks + type);
pid->nr = alloc_pidmap(); hlist_add_head_rcu(&pid->chain, pid_bucket(pid->nr)); }
return pid; }
void free_pid(struct pid_head *pid) { free_pidmap(pid->nr); kmem_cache_free(pid_cachep, pid); }
static struct pid_head *find_pid(pid_t nr) { struct hlist_node *node; struct pid_head *pid;
hlist_for_each_entry_rcu(pid, node, pid_bucket(nr), chain) if (pid->nr == nr) return pid;
return NULL; }
struct list_head *find_pid_list(enum pid_type type, pid_t nr) { struct pid_head *pid;
pid = find_pid(nr); if (pid) return pid->tasks + type;
return NULL; }
void attach_pid(struct task_struct *task, enum pid_type type, pid_t nr) { struct list_head *list;
list = find_pid_list(type, nr); BUG_ON(!list); list_add_tail_rcu(task->pids + type, list); }
static inline struct list_head *__detach_pid(struct task_struct *task, enum pid_type type) { struct list_head *list;
list = task->pids + type; list_del_rcu(list); // it doesn't touch ->next return list->next; }
void detach_pid(struct task_struct *task, enum pid_type type) { struct list_head *head; struct pid_head *pid;
head = __detach_pid(task, type); if (!list_empty(head)) return;
pid = list_entry(head, struct pid_head, tasks[type]);
for (type = 0; type < PIDTYPE_MAX; ++type) if (!list_empty(pid->tasks + type)) return;
free_pid(pid); }
We don't need ugly do_each_task_pid/while_each_task_pid anymore:
#define for_each_task_pid(head, pid, type, task) \ if ((head = find_pid_list(type, pid))) \ list_for_each_entry(task, head, pids[type])
And noe we can inplement pid_ref almost for free, just add ->count to 'struct pid_head'.
What do you think?
Oleg. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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