diff options
| -rw-r--r-- | fs/proc/base.c | 104 | ||||
| -rw-r--r-- | include/linux/pid.h | 1 | ||||
| -rw-r--r-- | include/linux/sched.h | 11 | ||||
| -rw-r--r-- | kernel/pid.c | 36 |
4 files changed, 83 insertions, 69 deletions
diff --git a/fs/proc/base.c b/fs/proc/base.c index 89c20d9d50bf..b18f3773dd43 100644 --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -2142,72 +2142,43 @@ out_no_task: } /* - * Find the first tgid to return to user space. + * Find the first task with tgid >= tgid * - * Usually this is just whatever follows &init_task, but if the users - * buffer was too small to hold the full list or there was a seek into - * the middle of the directory we have more work to do. - * - * In the case of a short read we start with find_task_by_pid. - * - * In the case of a seek we start with &init_task and walk nr - * threads past it. */ -static struct task_struct *first_tgid(int tgid, unsigned int nr) +static struct task_struct *next_tgid(unsigned int tgid) { - struct task_struct *pos; - rcu_read_lock(); - if (tgid && nr) { - pos = find_task_by_pid(tgid); - if (pos && thread_group_leader(pos)) - goto found; - } - /* If nr exceeds the number of processes get out quickly */ - pos = NULL; - if (nr && nr >= nr_processes()) - goto done; - - /* If we haven't found our starting place yet start with - * the init_task and walk nr tasks forward. - */ - for (pos = next_task(&init_task); nr > 0; --nr) { - pos = next_task(pos); - if (pos == &init_task) { - pos = NULL; - goto done; - } - } -found: - get_task_struct(pos); -done: - rcu_read_unlock(); - return pos; -} + struct task_struct *task; + struct pid *pid; -/* - * Find the next task in the task list. - * Return NULL if we loop or there is any error. - * - * The reference to the input task_struct is released. - */ -static struct task_struct *next_tgid(struct task_struct *start) -{ - struct task_struct *pos; rcu_read_lock(); - pos = start; - if (pid_alive(start)) - pos = next_task(start); - if (pid_alive(pos) && (pos != &init_task)) { - get_task_struct(pos); - goto done; +retry: + task = NULL; + pid = find_ge_pid(tgid); + if (pid) { + tgid = pid->nr + 1; + task = pid_task(pid, PIDTYPE_PID); + /* What we to know is if the pid we have find is the + * pid of a thread_group_leader. Testing for task + * being a thread_group_leader is the obvious thing + * todo but there is a window when it fails, due to + * the pid transfer logic in de_thread. + * + * So we perform the straight forward test of seeing + * if the pid we have found is the pid of a thread + * group leader, and don't worry if the task we have + * found doesn't happen to be a thread group leader. + * As we don't care in the case of readdir. + */ + if (!task || !has_group_leader_pid(task)) + goto retry; + get_task_struct(task); } - pos = NULL; -done: rcu_read_unlock(); - put_task_struct(start); - return pos; + return task; } +#define TGID_OFFSET (FIRST_PROCESS_ENTRY + (1 /* /proc/self */)) + /* for the /proc/ directory itself, after non-process stuff has been done */ int proc_pid_readdir(struct file * filp, void * dirent, filldir_t filldir) { @@ -2223,29 +2194,24 @@ int proc_pid_readdir(struct file * filp, void * dirent, filldir_t filldir) filp->f_pos++; nr++; } - nr -= 1; - /* f_version caches the tgid value that the last readdir call couldn't - * return. lseek aka telldir automagically resets f_version to 0. - */ - tgid = filp->f_version; - filp->f_version = 0; - for (task = first_tgid(tgid, nr); + tgid = filp->f_pos - TGID_OFFSET; + for (task = next_tgid(tgid); task; - task = next_tgid(task), filp->f_pos++) { + put_task_struct(task), task = next_tgid(tgid + 1)) { int len; ino_t ino; tgid = task->pid; + filp->f_pos = tgid + TGID_OFFSET; len = snprintf(buf, sizeof(buf), "%d", tgid); ino = fake_ino(tgid, PROC_TGID_INO); if (filldir(dirent, buf, len, filp->f_pos, ino, DT_DIR) < 0) { - /* returning this tgid failed, save it as the first - * pid for the next readir call */ - filp->f_version = tgid; put_task_struct(task); - break; + goto out; } } + filp->f_pos = PID_MAX_LIMIT + TGID_OFFSET; +out: return 0; } diff --git a/include/linux/pid.h b/include/linux/pid.h index 93da7e2d9f30..359121086de1 100644 --- a/include/linux/pid.h +++ b/include/linux/pid.h @@ -89,6 +89,7 @@ extern struct pid *FASTCALL(find_pid(int nr)); * Lookup a PID in the hash table, and return with it's count elevated. */ extern struct pid *find_get_pid(int nr); +extern struct pid *find_ge_pid(int nr); extern struct pid *alloc_pid(void); extern void FASTCALL(free_pid(struct pid *pid)); diff --git a/include/linux/sched.h b/include/linux/sched.h index 7ef899c47c29..be658e33bd26 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1358,6 +1358,17 @@ extern void wait_task_inactive(struct task_struct * p); /* de_thread depends on thread_group_leader not being a pid based check */ #define thread_group_leader(p) (p == p->group_leader) +/* Do to the insanities of de_thread it is possible for a process + * to have the pid of the thread group leader without actually being + * the thread group leader. For iteration through the pids in proc + * all we care about is that we have a task with the appropriate + * pid, we don't actually care if we have the right task. + */ +static inline int has_group_leader_pid(struct task_struct *p) +{ + return p->pid == p->tgid; +} + static inline struct task_struct *next_thread(const struct task_struct *p) { return list_entry(rcu_dereference(p->thread_group.next), diff --git a/kernel/pid.c b/kernel/pid.c index 8387e8c68193..ed89a732432c 100644 --- a/kernel/pid.c +++ b/kernel/pid.c @@ -145,6 +145,23 @@ static int alloc_pidmap(void) return -1; } +static int next_pidmap(int last) +{ + int offset; + pidmap_t *map; + + offset = (last + 1) & BITS_PER_PAGE_MASK; + map = &pidmap_array[(last + 1)/BITS_PER_PAGE]; + for (; map < &pidmap_array[PIDMAP_ENTRIES]; map++, offset = 0) { + if (unlikely(!map->page)) + continue; + offset = find_next_bit((map)->page, BITS_PER_PAGE, offset); + if (offset < BITS_PER_PAGE) + return mk_pid(map, offset); + } + return -1; +} + fastcall void put_pid(struct pid *pid) { if (!pid) @@ -303,6 +320,25 @@ struct pid *find_get_pid(pid_t nr) } /* + * Used by proc to find the first pid that is greater then or equal to nr. + * + * If there is a pid at nr this function is exactly the same as find_pid. + */ +struct pid *find_ge_pid(int nr) +{ + struct pid *pid; + + do { + pid = find_pid(nr); + if (pid) + break; + nr = next_pidmap(nr); + } while (nr > 0); + + return pid; +} + +/* * The pid hash table is scaled according to the amount of memory in the * machine. From a minimum of 16 slots up to 4096 slots at one gigabyte or * more. |