The patch titled
task: Make task list manipulations RCU safe
has been removed from the -mm tree. Its filename is
task-make-task-list-manipulations-rcu-safe.patch
This patch was probably dropped from -mm because
it has now been merged into a subsystem tree or
into Linus's tree, or because it was folded into
its parent patch in the -mm tree.
From: Eric W. Biederman <ebiederm@xxxxxxxxxxxx>
While we can currently walk through thread groups, process groups, and
sessions with just the rcu_read_lock, this opens the door to walking the
entire task list.
We already have all of the other RCU guarantees so there is no cost in
doing this, this should be enough so that proc can stop taking the tasklist
lock during readdir.
prev_task was killed because it has no users, and using it will miss new
tasks when doing an rcu traversal.
Signed-off-by: Eric W. Biederman <ebiederm@xxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxx>
---
fs/exec.c | 2 +-
include/linux/sched.h | 3 +--
kernel/exit.c | 2 +-
kernel/fork.c | 2 +-
4 files changed, 4 insertions(+), 5 deletions(-)
diff -puN fs/exec.c~task-make-task-list-manipulations-rcu-safe fs/exec.c
--- devel/fs/exec.c~task-make-task-list-manipulations-rcu-safe 2006-04-18 22:19:57.000000000 -0700
+++ devel-akpm/fs/exec.c 2006-04-18 22:19:57.000000000 -0700
@@ -712,7 +712,7 @@ static int de_thread(struct task_struct
attach_pid(current, PIDTYPE_PID, current->pid);
attach_pid(current, PIDTYPE_PGID, current->signal->pgrp);
attach_pid(current, PIDTYPE_SID, current->signal->session);
- list_add_tail(¤t->tasks, &init_task.tasks);
+ list_add_tail_rcu(¤t->tasks, &init_task.tasks);
current->group_leader = current;
leader->group_leader = current;
diff -puN include/linux/sched.h~task-make-task-list-manipulations-rcu-safe include/linux/sched.h
--- devel/include/linux/sched.h~task-make-task-list-manipulations-rcu-safe 2006-04-18 22:19:57.000000000 -0700
+++ devel-akpm/include/linux/sched.h 2006-04-18 22:19:57.000000000 -0700
@@ -1192,8 +1192,7 @@ extern void wait_task_inactive(task_t *
#define remove_parent(p) list_del_init(&(p)->sibling)
#define add_parent(p) list_add_tail(&(p)->sibling,&(p)->parent->children)
-#define next_task(p) list_entry((p)->tasks.next, struct task_struct, tasks)
-#define prev_task(p) list_entry((p)->tasks.prev, struct task_struct, tasks)
+#define next_task(p) list_entry(rcu_dereference((p)->tasks.next), struct task_struct, tasks)
#define for_each_process(p) \
for (p = &init_task ; (p = next_task(p)) != &init_task ; )
diff -puN kernel/exit.c~task-make-task-list-manipulations-rcu-safe kernel/exit.c
--- devel/kernel/exit.c~task-make-task-list-manipulations-rcu-safe 2006-04-18 22:19:57.000000000 -0700
+++ devel-akpm/kernel/exit.c 2006-04-18 22:19:57.000000000 -0700
@@ -56,7 +56,7 @@ static void __unhash_process(struct task
detach_pid(p, PIDTYPE_PGID);
detach_pid(p, PIDTYPE_SID);
- list_del_init(&p->tasks);
+ list_del_rcu(&p->tasks);
__get_cpu_var(process_counts)--;
}
list_del_rcu(&p->thread_group);
diff -puN kernel/fork.c~task-make-task-list-manipulations-rcu-safe kernel/fork.c
--- devel/kernel/fork.c~task-make-task-list-manipulations-rcu-safe 2006-04-18 22:19:57.000000000 -0700
+++ devel-akpm/kernel/fork.c 2006-04-18 22:19:57.000000000 -0700
@@ -1204,7 +1204,7 @@ static task_t *copy_process(unsigned lon
attach_pid(p, PIDTYPE_PGID, process_group(p));
attach_pid(p, PIDTYPE_SID, p->signal->session);
- list_add_tail(&p->tasks, &init_task.tasks);
+ list_add_tail_rcu(&p->tasks, &init_task.tasks);
__get_cpu_var(process_counts)++;
}
attach_pid(p, PIDTYPE_PID, p->pid);
_
Patches currently in -mm which might be from ebiederm@xxxxxxxxxxxx are
origin.patch
avoid-tasklist_lock-at-getrusage-for-multithreaded-case-too.patch
ptrace-document-the-locking-rules.patch
proc-fix-the-inode-number-on-proc-pid-fd.patch
proc-remove-useless-bkl-in-proc_pid_readlink.patch
proc-remove-unnecessary-and-misleading-assignments.patch
proc-simplify-the-ownership-rules-for-proc.patch
proc-replace-proc_inodetype-with-proc_inodefd.patch
proc-remove-bogus-proc_task_permission.patch
proc-kill-proc_mem_inode_operations.patch
proc-properly-filter-out-files-that-are-not-visible.patch
proc-fix-the-link-count-for-proc-pid-task.patch
proc-move-proc_maps_operations-into-task_mmuc.patch
proc-rewrite-the-proc-dentry-flush-on-exit.patch
proc-close-the-race-of-a-process-dying-durning.patch
proc-refactor-reading-directories-of-tasks.patch
proc-remove-tasklist_lock-from-proc_pid_readdir.patch
proc-remove-tasklist_lock-from-proc_pid_lookup-and.patch
proc-remove-tasklist_lock-from-proc_pid_readdir-simply-fix-first_tgid.patch
proc-make-proc_numbuf-the-buffer-size-for-holding-a.patch
proc-dont-lock-task_structs-indefinitely.patch
proc-use-struct-pid-not-struct-task_ref.patch
proc-optimize-proc_check_dentry_visible.patch
proc-use-sane-permission-checks-on-the-proc-pid-fd.patch
proc-cleanup-proc_fd_access_allowed.patch
proc-remove-tasklist_lock-from-proc_task_readdir.patch
simplify-fix-first_tid.patch
cleanup-next_tid.patch
coredump-optimize-mm-users-traversal.patch
coredump-speedup-sigkill-sending.patch
coredump-kill-ptrace-related-stuff.patch
coredump-dont-take-tasklist_lock.patch
pidhash-temporary-debug-checks.patch
-
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