Messages in this thread Patch in this message | | | Date | Thu, 24 Aug 2006 21:01:36 +0900 | From | KAMEZAWA Hiroyuki <> | Subject | [RFC][PATCH] ps command race fix take 3 [2/4] add member to task struct |
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add watch_head to task_struct. This is used by /proc/<pid> readdir() routine.
pointer from /proc (which traverse task_list) is moved to next_task() if target task is removed.
Note: next_task() in release_task() never return stale task struct.
Signed-Off-By: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
include/linux/init_task.h | 2 ++ include/linux/sched.h | 4 +++- kernel/exit.c | 7 ++++++- kernel/fork.c | 3 +++ 4 files changed, 14 insertions(+), 2 deletions(-)
Index: linux-2.6.18-rc4/include/linux/sched.h =================================================================== --- linux-2.6.18-rc4.orig/include/linux/sched.h +++ linux-2.6.18-rc4/include/linux/sched.h @@ -80,6 +80,7 @@ struct sched_param { #include <linux/resource.h> #include <linux/timer.h> #include <linux/hrtimer.h> +#include <linux/watch_head.h> #include <asm/processor.h> @@ -988,7 +989,8 @@ struct task_struct { atomic_t fs_excl; /* holding fs exclusive resources */ struct rcu_head rcu; - + /* used by /proc/<pid> */ + struct watch_head watch; /* * cache last used pipe for splice */ Index: linux-2.6.18-rc4/kernel/fork.c =================================================================== --- linux-2.6.18-rc4.orig/kernel/fork.c +++ linux-2.6.18-rc4/kernel/fork.c @@ -45,6 +45,7 @@ #include <linux/cn_proc.h> #include <linux/delayacct.h> #include <linux/taskstats_kern.h> +#include <linux/watch_head.h> #include <asm/pgtable.h> #include <asm/pgalloc.h> @@ -1154,6 +1155,7 @@ static struct task_struct *copy_process( INIT_LIST_HEAD(&p->thread_group); INIT_LIST_HEAD(&p->ptrace_children); INIT_LIST_HEAD(&p->ptrace_list); + init_watch(&p->watch); /* Perform scheduler related setup. Assign this task to a CPU. */ sched_fork(p, clone_flags); @@ -1241,6 +1243,7 @@ static struct task_struct *copy_process( __get_cpu_var(process_counts)++; } attach_pid(p, PIDTYPE_PID, p->pid); + make_watch_ready(&p->watch); nr_threads++; } Index: linux-2.6.18-rc4/include/linux/init_task.h =================================================================== --- linux-2.6.18-rc4.orig/include/linux/init_task.h +++ linux-2.6.18-rc4/include/linux/init_task.h @@ -5,6 +5,7 @@ #include <linux/rcupdate.h> #include <linux/irqflags.h> #include <linux/lockdep.h> +#include <linux/watch_head.h> #define INIT_FDTABLE \ { \ @@ -128,6 +129,7 @@ extern struct group_info init_groups; .pi_lock = SPIN_LOCK_UNLOCKED, \ INIT_TRACE_IRQFLAGS \ INIT_LOCKDEP \ + .watch = WATCH_HEAD_INIT(tsk.watch), \ } Index: linux-2.6.18-rc4/kernel/exit.c =================================================================== --- linux-2.6.18-rc4.orig/kernel/exit.c +++ linux-2.6.18-rc4/kernel/exit.c @@ -38,6 +38,7 @@ #include <linux/pipe_fs_i.h> #include <linux/audit.h> /* for audit_free() */ #include <linux/resource.h> +#include <linux/watch_head.h> #include <asm/uaccess.h> #include <asm/unistd.h> @@ -136,13 +137,17 @@ static void delayed_put_task_struct(stru void release_task(struct task_struct * p) { - struct task_struct *leader; + struct task_struct *leader, *next; int zap_leader; repeat: atomic_dec(&p->user->processes); write_lock_irq(&tasklist_lock); ptrace_unlink(p); BUG_ON(!list_empty(&p->ptrace_list) || !list_empty(&p->ptrace_children)); + + /* move pointer from /proc to next task */ + next = next_task(p); + move_watcher(&p->watch, &next->watch); __exit_signal(p); /* - 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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