From 2f7ee5691eecb67c8108b92001a85563ea336ac5 Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Mon, 12 Dec 2011 18:12:21 -0800 Subject: cgroup: introduce cgroup_taskset and use it in subsys->can_attach(), cancel_attach() and attach() Currently, there's no way to pass multiple tasks to cgroup_subsys methods necessitating the need for separate per-process and per-task methods. This patch introduces cgroup_taskset which can be used to pass multiple tasks and their associated cgroups to cgroup_subsys methods. Three methods - can_attach(), cancel_attach() and attach() - are converted to use cgroup_taskset. This unifies passed parameters so that all methods have access to all information. Conversions in this patchset are identical and don't introduce any behavior change. -v2: documentation updated as per Paul Menage's suggestion. Signed-off-by: Tejun Heo Reviewed-by: KAMEZAWA Hiroyuki Reviewed-by: Frederic Weisbecker Acked-by: Paul Menage Acked-by: Li Zefan Cc: Balbir Singh Cc: Daisuke Nishimura Cc: KAMEZAWA Hiroyuki Cc: James Morris --- Documentation/cgroups/cgroups.txt | 31 +++++++++++++++++++++---------- 1 file changed, 21 insertions(+), 10 deletions(-) (limited to 'Documentation/cgroups') diff --git a/Documentation/cgroups/cgroups.txt b/Documentation/cgroups/cgroups.txt index 9c452ef2328..8a2f302327f 100644 --- a/Documentation/cgroups/cgroups.txt +++ b/Documentation/cgroups/cgroups.txt @@ -594,15 +594,25 @@ rmdir() will fail with it. From this behavior, pre_destroy() can be called multiple times against a cgroup. int can_attach(struct cgroup_subsys *ss, struct cgroup *cgrp, - struct task_struct *task) + struct cgroup_taskset *tset) (cgroup_mutex held by caller) -Called prior to moving a task into a cgroup; if the subsystem -returns an error, this will abort the attach operation. If a NULL -task is passed, then a successful result indicates that *any* -unspecified task can be moved into the cgroup. Note that this isn't -called on a fork. If this method returns 0 (success) then this should -remain valid while the caller holds cgroup_mutex and it is ensured that either +Called prior to moving one or more tasks into a cgroup; if the +subsystem returns an error, this will abort the attach operation. +@tset contains the tasks to be attached and is guaranteed to have at +least one task in it. + +If there are multiple tasks in the taskset, then: + - it's guaranteed that all are from the same thread group + - @tset contains all tasks from the thread group whether or not + they're switching cgroups + - the first task is the leader + +Each @tset entry also contains the task's old cgroup and tasks which +aren't switching cgroup can be skipped easily using the +cgroup_taskset_for_each() iterator. Note that this isn't called on a +fork. If this method returns 0 (success) then this should remain valid +while the caller holds cgroup_mutex and it is ensured that either attach() or cancel_attach() will be called in future. int can_attach_task(struct cgroup *cgrp, struct task_struct *tsk); @@ -613,14 +623,14 @@ attached (possibly many when using cgroup_attach_proc). Called after can_attach. void cancel_attach(struct cgroup_subsys *ss, struct cgroup *cgrp, - struct task_struct *task, bool threadgroup) + struct cgroup_taskset *tset) (cgroup_mutex held by caller) Called when a task attach operation has failed after can_attach() has succeeded. A subsystem whose can_attach() has some side-effects should provide this function, so that the subsystem can implement a rollback. If not, not necessary. This will be called only about subsystems whose can_attach() operation have -succeeded. +succeeded. The parameters are identical to can_attach(). void pre_attach(struct cgroup *cgrp); (cgroup_mutex held by caller) @@ -629,11 +639,12 @@ For any non-per-thread attachment work that needs to happen before attach_task. Needed by cpuset. void attach(struct cgroup_subsys *ss, struct cgroup *cgrp, - struct cgroup *old_cgrp, struct task_struct *task) + struct cgroup_taskset *tset) (cgroup_mutex held by caller) Called after the task has been attached to the cgroup, to allow any post-attachment activity that requires memory allocations or blocking. +The parameters are identical to can_attach(). void attach_task(struct cgroup *cgrp, struct task_struct *tsk); (cgroup_mutex held by caller) -- cgit v1.2.3 From 494c167cf76d02000adf740c215adc69a824ecc9 Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Mon, 12 Dec 2011 18:12:22 -0800 Subject: cgroup: kill subsys->can_attach_task(), pre_attach() and attach_task() These three methods are no longer used. Kill them. Signed-off-by: Tejun Heo Reviewed-by: KAMEZAWA Hiroyuki Reviewed-by: Frederic Weisbecker Acked-by: Paul Menage Cc: Li Zefan --- Documentation/cgroups/cgroups.txt | 20 --------------- include/linux/cgroup.h | 3 --- kernel/cgroup.c | 52 ++++----------------------------------- 3 files changed, 5 insertions(+), 70 deletions(-) (limited to 'Documentation/cgroups') diff --git a/Documentation/cgroups/cgroups.txt b/Documentation/cgroups/cgroups.txt index 8a2f302327f..a7c96ae5557 100644 --- a/Documentation/cgroups/cgroups.txt +++ b/Documentation/cgroups/cgroups.txt @@ -615,13 +615,6 @@ fork. If this method returns 0 (success) then this should remain valid while the caller holds cgroup_mutex and it is ensured that either attach() or cancel_attach() will be called in future. -int can_attach_task(struct cgroup *cgrp, struct task_struct *tsk); -(cgroup_mutex held by caller) - -As can_attach, but for operations that must be run once per task to be -attached (possibly many when using cgroup_attach_proc). Called after -can_attach. - void cancel_attach(struct cgroup_subsys *ss, struct cgroup *cgrp, struct cgroup_taskset *tset) (cgroup_mutex held by caller) @@ -632,12 +625,6 @@ function, so that the subsystem can implement a rollback. If not, not necessary. This will be called only about subsystems whose can_attach() operation have succeeded. The parameters are identical to can_attach(). -void pre_attach(struct cgroup *cgrp); -(cgroup_mutex held by caller) - -For any non-per-thread attachment work that needs to happen before -attach_task. Needed by cpuset. - void attach(struct cgroup_subsys *ss, struct cgroup *cgrp, struct cgroup_taskset *tset) (cgroup_mutex held by caller) @@ -646,13 +633,6 @@ Called after the task has been attached to the cgroup, to allow any post-attachment activity that requires memory allocations or blocking. The parameters are identical to can_attach(). -void attach_task(struct cgroup *cgrp, struct task_struct *tsk); -(cgroup_mutex held by caller) - -As attach, but for operations that must be run once per task to be attached, -like can_attach_task. Called before attach. Currently does not support any -subsystem that might need the old_cgrp for every thread in the group. - void fork(struct cgroup_subsy *ss, struct task_struct *task) Called when a task is forked into a cgroup. diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h index 34256ad9e55..7ad5e406c42 100644 --- a/include/linux/cgroup.h +++ b/include/linux/cgroup.h @@ -490,11 +490,8 @@ struct cgroup_subsys { void (*destroy)(struct cgroup_subsys *ss, struct cgroup *cgrp); int (*can_attach)(struct cgroup_subsys *ss, struct cgroup *cgrp, struct cgroup_taskset *tset); - int (*can_attach_task)(struct cgroup *cgrp, struct task_struct *tsk); void (*cancel_attach)(struct cgroup_subsys *ss, struct cgroup *cgrp, struct cgroup_taskset *tset); - void (*pre_attach)(struct cgroup *cgrp); - void (*attach_task)(struct cgroup *cgrp, struct task_struct *tsk); void (*attach)(struct cgroup_subsys *ss, struct cgroup *cgrp, struct cgroup_taskset *tset); void (*fork)(struct cgroup_subsys *ss, struct task_struct *task); diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 41ee01e392e..1b3b84174ea 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -1944,13 +1944,6 @@ int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk) goto out; } } - if (ss->can_attach_task) { - retval = ss->can_attach_task(cgrp, tsk); - if (retval) { - failed_ss = ss; - goto out; - } - } } retval = cgroup_task_migrate(cgrp, oldcgrp, tsk, false); @@ -1958,10 +1951,6 @@ int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk) goto out; for_each_subsys(root, ss) { - if (ss->pre_attach) - ss->pre_attach(cgrp); - if (ss->attach_task) - ss->attach_task(cgrp, tsk); if (ss->attach) ss->attach(ss, cgrp, &tset); } @@ -2093,7 +2082,6 @@ int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader) { int retval, i, group_size, nr_migrating_tasks; struct cgroup_subsys *ss, *failed_ss = NULL; - bool cancel_failed_ss = false; /* guaranteed to be initialized later, but the compiler needs this */ struct css_set *oldcg; struct cgroupfs_root *root = cgrp->root; @@ -2188,21 +2176,6 @@ int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader) goto out_cancel_attach; } } - /* a callback to be run on every thread in the threadgroup. */ - if (ss->can_attach_task) { - /* run on each task in the threadgroup. */ - for (i = 0; i < group_size; i++) { - tc = flex_array_get(group, i); - if (tc->cgrp == cgrp) - continue; - retval = ss->can_attach_task(cgrp, tc->task); - if (retval) { - failed_ss = ss; - cancel_failed_ss = true; - goto out_cancel_attach; - } - } - } } /* @@ -2234,15 +2207,10 @@ int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader) } /* - * step 3: now that we're guaranteed success wrt the css_sets, proceed - * to move all tasks to the new cgroup, calling ss->attach_task for each - * one along the way. there are no failure cases after here, so this is - * the commit point. + * step 3: now that we're guaranteed success wrt the css_sets, + * proceed to move all tasks to the new cgroup. There are no + * failure cases after here, so this is the commit point. */ - for_each_subsys(root, ss) { - if (ss->pre_attach) - ss->pre_attach(cgrp); - } for (i = 0; i < group_size; i++) { tc = flex_array_get(group, i); /* leave current thread as it is if it's already there */ @@ -2250,18 +2218,11 @@ int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader) continue; retval = cgroup_task_migrate(cgrp, tc->cgrp, tc->task, true); BUG_ON(retval); - /* attach each task to each subsystem */ - for_each_subsys(root, ss) { - if (ss->attach_task) - ss->attach_task(cgrp, tc->task); - } } /* nothing is sensitive to fork() after this point. */ /* - * step 4: do expensive, non-thread-specific subsystem callbacks. - * TODO: if ever a subsystem needs to know the oldcgrp for each task - * being moved, this call will need to be reworked to communicate that. + * step 4: do subsystem attach callbacks. */ for_each_subsys(root, ss) { if (ss->attach) @@ -2285,11 +2246,8 @@ out_cancel_attach: /* same deal as in cgroup_attach_task */ if (retval) { for_each_subsys(root, ss) { - if (ss == failed_ss) { - if (cancel_failed_ss && ss->cancel_attach) - ss->cancel_attach(ss, cgrp, &tset); + if (ss == failed_ss) break; - } if (ss->cancel_attach) ss->cancel_attach(ss, cgrp, &tset); } -- cgit v1.2.3