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sched/cpuset: Bring back cpuset_mutex

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Turns out percpu_cpuset_rwsem - commit 1243dc518c ("cgroup/cpuset:
Convert cpuset_mutex to percpu_rwsem") - wasn't such a brilliant idea,
as it has been reported to cause slowdowns in workloads that need to
change cpuset configuration frequently and it is also not implementing
priority inheritance (which causes troubles with realtime workloads).

Convert percpu_cpuset_rwsem back to regular cpuset_mutex. Also grab it
only for SCHED_DEADLINE tasks (other policies don't care about stable
cpusets anyway).

Signed-off-by: Juri Lelli <juri.lelli@redhat.com>
Reviewed-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Juri Lelli 2023-05-08 09:58:50 +02:00 committed by Tejun Heo
parent ad3a557daf
commit 111cd11bbc
3 changed files with 99 additions and 90 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
include/linux/cpuset.h
View File

@ -71,8 +71,8 @@ extern void cpuset_init_smp(void);
extern void cpuset_force_rebuild(void); extern void cpuset_force_rebuild(void);
extern void cpuset_update_active_cpus(void); extern void cpuset_update_active_cpus(void);
extern void cpuset_wait_for_hotplug(void); extern void cpuset_wait_for_hotplug(void);
extern void cpuset_read_lock(void); extern void cpuset_lock(void);
extern void cpuset_read_unlock(void); extern void cpuset_unlock(void);
extern void cpuset_cpus_allowed(struct task_struct *p, struct cpumask *mask); extern void cpuset_cpus_allowed(struct task_struct *p, struct cpumask *mask);
extern bool cpuset_cpus_allowed_fallback(struct task_struct *p); extern bool cpuset_cpus_allowed_fallback(struct task_struct *p);
extern nodemask_t cpuset_mems_allowed(struct task_struct *p); extern nodemask_t cpuset_mems_allowed(struct task_struct *p);
@ -189,8 +189,8 @@ static inline void cpuset_update_active_cpus(void)
static inline void cpuset_wait_for_hotplug(void) { } static inline void cpuset_wait_for_hotplug(void) { }
static inline void cpuset_read_lock(void) { } static inline void cpuset_lock(void) { }
static inline void cpuset_read_unlock(void) { } static inline void cpuset_unlock(void) { }
static inline void cpuset_cpus_allowed(struct task_struct *p, static inline void cpuset_cpus_allowed(struct task_struct *p,
struct cpumask *mask) struct cpumask *mask)

159
kernel/cgroup/cpuset.c
View File

@ -366,22 +366,23 @@ static struct cpuset top_cpuset = {
if (is_cpuset_online(((des_cs) = css_cs((pos_css))))) if (is_cpuset_online(((des_cs) = css_cs((pos_css)))))
/* /*
* There are two global locks guarding cpuset structures - cpuset_rwsem and * There are two global locks guarding cpuset structures - cpuset_mutex and
* callback_lock. We also require taking task_lock() when dereferencing a * callback_lock. We also require taking task_lock() when dereferencing a
* task's cpuset pointer. See "The task_lock() exception", at the end of this * task's cpuset pointer. See "The task_lock() exception", at the end of this
* comment. The cpuset code uses only cpuset_rwsem write lock. Other * comment. The cpuset code uses only cpuset_mutex. Other kernel subsystems
* kernel subsystems can use cpuset_read_lock()/cpuset_read_unlock() to * can use cpuset_lock()/cpuset_unlock() to prevent change to cpuset
* prevent change to cpuset structures. * structures. Note that cpuset_mutex needs to be a mutex as it is used in
* paths that rely on priority inheritance (e.g. scheduler - on RT) for
* correctness.
* *
* A task must hold both locks to modify cpusets. If a task holds * A task must hold both locks to modify cpusets. If a task holds
* cpuset_rwsem, it blocks others wanting that rwsem, ensuring that it * cpuset_mutex, it blocks others, ensuring that it is the only task able to
* is the only task able to also acquire callback_lock and be able to * also acquire callback_lock and be able to modify cpusets. It can perform
* modify cpusets. It can perform various checks on the cpuset structure * various checks on the cpuset structure first, knowing nothing will change.
* first, knowing nothing will change. It can also allocate memory while * It can also allocate memory while just holding cpuset_mutex. While it is
* just holding cpuset_rwsem. While it is performing these checks, various * performing these checks, various callback routines can briefly acquire
* callback routines can briefly acquire callback_lock to query cpusets. * callback_lock to query cpusets. Once it is ready to make the changes, it
* Once it is ready to make the changes, it takes callback_lock, blocking * takes callback_lock, blocking everyone else.
* everyone else.
* *
* Calls to the kernel memory allocator can not be made while holding * Calls to the kernel memory allocator can not be made while holding
* callback_lock, as that would risk double tripping on callback_lock * callback_lock, as that would risk double tripping on callback_lock
@ -403,16 +404,16 @@ static struct cpuset top_cpuset = {
* guidelines for accessing subsystem state in kernel/cgroup.c * guidelines for accessing subsystem state in kernel/cgroup.c
*/ */
DEFINE_STATIC_PERCPU_RWSEM(cpuset_rwsem); static DEFINE_MUTEX(cpuset_mutex);
void cpuset_read_lock(void) void cpuset_lock(void)
{ {
percpu_down_read(&cpuset_rwsem); mutex_lock(&cpuset_mutex);
} }
void cpuset_read_unlock(void) void cpuset_unlock(void)
{ {
percpu_up_read(&cpuset_rwsem); mutex_unlock(&cpuset_mutex);
} }
static DEFINE_SPINLOCK(callback_lock); static DEFINE_SPINLOCK(callback_lock);
@ -496,7 +497,7 @@ static inline bool partition_is_populated(struct cpuset *cs,
* One way or another, we guarantee to return some non-empty subset * One way or another, we guarantee to return some non-empty subset
* of cpu_online_mask. * of cpu_online_mask.
* *
* Call with callback_lock or cpuset_rwsem held. * Call with callback_lock or cpuset_mutex held.
*/ */
static void guarantee_online_cpus(struct task_struct *tsk, static void guarantee_online_cpus(struct task_struct *tsk,
struct cpumask *pmask) struct cpumask *pmask)
@ -538,7 +539,7 @@ static void guarantee_online_cpus(struct task_struct *tsk,
* One way or another, we guarantee to return some non-empty subset * One way or another, we guarantee to return some non-empty subset
* of node_states[N_MEMORY]. * of node_states[N_MEMORY].
* *
* Call with callback_lock or cpuset_rwsem held. * Call with callback_lock or cpuset_mutex held.
*/ */
static void guarantee_online_mems(struct cpuset *cs, nodemask_t *pmask) static void guarantee_online_mems(struct cpuset *cs, nodemask_t *pmask)
{ {
@ -550,7 +551,7 @@ static void guarantee_online_mems(struct cpuset *cs, nodemask_t *pmask)
/* /*
* update task's spread flag if cpuset's page/slab spread flag is set * update task's spread flag if cpuset's page/slab spread flag is set
* *
* Call with callback_lock or cpuset_rwsem held. The check can be skipped * Call with callback_lock or cpuset_mutex held. The check can be skipped
* if on default hierarchy. * if on default hierarchy.
*/ */
static void cpuset_update_task_spread_flags(struct cpuset *cs, static void cpuset_update_task_spread_flags(struct cpuset *cs,
@ -575,7 +576,7 @@ static void cpuset_update_task_spread_flags(struct cpuset *cs,
* *
* One cpuset is a subset of another if all its allowed CPUs and * One cpuset is a subset of another if all its allowed CPUs and
* Memory Nodes are a subset of the other, and its exclusive flags * Memory Nodes are a subset of the other, and its exclusive flags
* are only set if the other's are set. Call holding cpuset_rwsem. * are only set if the other's are set. Call holding cpuset_mutex.
*/ */
static int is_cpuset_subset(const struct cpuset *p, const struct cpuset *q) static int is_cpuset_subset(const struct cpuset *p, const struct cpuset *q)
@ -713,7 +714,7 @@ static int validate_change_legacy(struct cpuset *cur, struct cpuset *trial)
* If we replaced the flag and mask values of the current cpuset * If we replaced the flag and mask values of the current cpuset
* (cur) with those values in the trial cpuset (trial), would * (cur) with those values in the trial cpuset (trial), would
* our various subset and exclusive rules still be valid? Presumes * our various subset and exclusive rules still be valid? Presumes
* cpuset_rwsem held. * cpuset_mutex held.
* *
* 'cur' is the address of an actual, in-use cpuset. Operations * 'cur' is the address of an actual, in-use cpuset. Operations
* such as list traversal that depend on the actual address of the * such as list traversal that depend on the actual address of the
@ -829,7 +830,7 @@ static void update_domain_attr_tree(struct sched_domain_attr *dattr,
rcu_read_unlock(); rcu_read_unlock();
} }
/* Must be called with cpuset_rwsem held. */ /* Must be called with cpuset_mutex held. */
static inline int nr_cpusets(void) static inline int nr_cpusets(void)
{ {
/* jump label reference count + the top-level cpuset */ /* jump label reference count + the top-level cpuset */
@ -855,7 +856,7 @@ static inline int nr_cpusets(void)
* domains when operating in the severe memory shortage situations * domains when operating in the severe memory shortage situations
* that could cause allocation failures below. * that could cause allocation failures below.
* *
* Must be called with cpuset_rwsem held. * Must be called with cpuset_mutex held.
* *
* The three key local variables below are: * The three key local variables below are:
* cp - cpuset pointer, used (together with pos_css) to perform a * cp - cpuset pointer, used (together with pos_css) to perform a
@ -1084,7 +1085,7 @@ static void dl_rebuild_rd_accounting(void)
struct cpuset *cs = NULL; struct cpuset *cs = NULL;
struct cgroup_subsys_state *pos_css; struct cgroup_subsys_state *pos_css;
percpu_rwsem_assert_held(&cpuset_rwsem); lockdep_assert_held(&cpuset_mutex);
lockdep_assert_cpus_held(); lockdep_assert_cpus_held();
lockdep_assert_held(&sched_domains_mutex); lockdep_assert_held(&sched_domains_mutex);
@ -1134,7 +1135,7 @@ partition_and_rebuild_sched_domains(int ndoms_new, cpumask_var_t doms_new[],
* 'cpus' is removed, then call this routine to rebuild the * 'cpus' is removed, then call this routine to rebuild the
* scheduler's dynamic sched domains. * scheduler's dynamic sched domains.
* *
* Call with cpuset_rwsem held. Takes cpus_read_lock(). * Call with cpuset_mutex held. Takes cpus_read_lock().
*/ */
static void rebuild_sched_domains_locked(void) static void rebuild_sched_domains_locked(void)
{ {
@ -1145,7 +1146,7 @@ static void rebuild_sched_domains_locked(void)
int ndoms; int ndoms;
lockdep_assert_cpus_held(); lockdep_assert_cpus_held();
percpu_rwsem_assert_held(&cpuset_rwsem); lockdep_assert_held(&cpuset_mutex);
/* /*
* If we have raced with CPU hotplug, return early to avoid * If we have raced with CPU hotplug, return early to avoid
@ -1196,9 +1197,9 @@ static void rebuild_sched_domains_locked(void)
void rebuild_sched_domains(void) void rebuild_sched_domains(void)
{ {
cpus_read_lock(); cpus_read_lock();
percpu_down_write(&cpuset_rwsem); mutex_lock(&cpuset_mutex);
rebuild_sched_domains_locked(); rebuild_sched_domains_locked();
percpu_up_write(&cpuset_rwsem); mutex_unlock(&cpuset_mutex);
cpus_read_unlock(); cpus_read_unlock();
} }
@ -1208,7 +1209,7 @@ void rebuild_sched_domains(void)
* @new_cpus: the temp variable for the new effective_cpus mask * @new_cpus: the temp variable for the new effective_cpus mask
* *
* Iterate through each task of @cs updating its cpus_allowed to the * Iterate through each task of @cs updating its cpus_allowed to the
* effective cpuset's. As this function is called with cpuset_rwsem held, * effective cpuset's. As this function is called with cpuset_mutex held,
* cpuset membership stays stable. For top_cpuset, task_cpu_possible_mask() * cpuset membership stays stable. For top_cpuset, task_cpu_possible_mask()
* is used instead of effective_cpus to make sure all offline CPUs are also * is used instead of effective_cpus to make sure all offline CPUs are also
* included as hotplug code won't update cpumasks for tasks in top_cpuset. * included as hotplug code won't update cpumasks for tasks in top_cpuset.
@ -1322,7 +1323,7 @@ static int update_parent_subparts_cpumask(struct cpuset *cs, int cmd,
int old_prs, new_prs; int old_prs, new_prs;
int part_error = PERR_NONE; /* Partition error? */ int part_error = PERR_NONE; /* Partition error? */
percpu_rwsem_assert_held(&cpuset_rwsem); lockdep_assert_held(&cpuset_mutex);
/* /*
* The parent must be a partition root. * The parent must be a partition root.
@ -1545,7 +1546,7 @@ static int update_parent_subparts_cpumask(struct cpuset *cs, int cmd,
* *
* On legacy hierarchy, effective_cpus will be the same with cpu_allowed. * On legacy hierarchy, effective_cpus will be the same with cpu_allowed.
* *
* Called with cpuset_rwsem held * Called with cpuset_mutex held
*/ */
static void update_cpumasks_hier(struct cpuset *cs, struct tmpmasks *tmp, static void update_cpumasks_hier(struct cpuset *cs, struct tmpmasks *tmp,
bool force) bool force)
@ -1705,7 +1706,7 @@ static void update_sibling_cpumasks(struct cpuset *parent, struct cpuset *cs,
struct cpuset *sibling; struct cpuset *sibling;
struct cgroup_subsys_state *pos_css; struct cgroup_subsys_state *pos_css;
percpu_rwsem_assert_held(&cpuset_rwsem); lockdep_assert_held(&cpuset_mutex);
/* /*
* Check all its siblings and call update_cpumasks_hier() * Check all its siblings and call update_cpumasks_hier()
@ -1955,12 +1956,12 @@ static void *cpuset_being_rebound;
* @cs: the cpuset in which each task's mems_allowed mask needs to be changed * @cs: the cpuset in which each task's mems_allowed mask needs to be changed
* *
* Iterate through each task of @cs updating its mems_allowed to the * Iterate through each task of @cs updating its mems_allowed to the
* effective cpuset's. As this function is called with cpuset_rwsem held, * effective cpuset's. As this function is called with cpuset_mutex held,
* cpuset membership stays stable. * cpuset membership stays stable.
*/ */
static void update_tasks_nodemask(struct cpuset *cs) static void update_tasks_nodemask(struct cpuset *cs)
{ {
static nodemask_t newmems; /* protected by cpuset_rwsem */ static nodemask_t newmems; /* protected by cpuset_mutex */
struct css_task_iter it; struct css_task_iter it;
struct task_struct *task; struct task_struct *task;
@ -1973,7 +1974,7 @@ static void update_tasks_nodemask(struct cpuset *cs)
* take while holding tasklist_lock. Forks can happen - the * take while holding tasklist_lock. Forks can happen - the
* mpol_dup() cpuset_being_rebound check will catch such forks, * mpol_dup() cpuset_being_rebound check will catch such forks,
* and rebind their vma mempolicies too. Because we still hold * and rebind their vma mempolicies too. Because we still hold
* the global cpuset_rwsem, we know that no other rebind effort * the global cpuset_mutex, we know that no other rebind effort
* will be contending for the global variable cpuset_being_rebound. * will be contending for the global variable cpuset_being_rebound.
* It's ok if we rebind the same mm twice; mpol_rebind_mm() * It's ok if we rebind the same mm twice; mpol_rebind_mm()
* is idempotent. Also migrate pages in each mm to new nodes. * is idempotent. Also migrate pages in each mm to new nodes.
@ -2019,7 +2020,7 @@ static void update_tasks_nodemask(struct cpuset *cs)
* *
* On legacy hierarchy, effective_mems will be the same with mems_allowed. * On legacy hierarchy, effective_mems will be the same with mems_allowed.
* *
* Called with cpuset_rwsem held * Called with cpuset_mutex held
*/ */
static void update_nodemasks_hier(struct cpuset *cs, nodemask_t *new_mems) static void update_nodemasks_hier(struct cpuset *cs, nodemask_t *new_mems)
{ {
@ -2072,7 +2073,7 @@ static void update_nodemasks_hier(struct cpuset *cs, nodemask_t *new_mems)
* mempolicies and if the cpuset is marked 'memory_migrate', * mempolicies and if the cpuset is marked 'memory_migrate',
* migrate the tasks pages to the new memory. * migrate the tasks pages to the new memory.
* *
* Call with cpuset_rwsem held. May take callback_lock during call. * Call with cpuset_mutex held. May take callback_lock during call.
* Will take tasklist_lock, scan tasklist for tasks in cpuset cs, * Will take tasklist_lock, scan tasklist for tasks in cpuset cs,
* lock each such tasks mm->mmap_lock, scan its vma's and rebind * lock each such tasks mm->mmap_lock, scan its vma's and rebind
* their mempolicies to the cpusets new mems_allowed. * their mempolicies to the cpusets new mems_allowed.
@ -2164,7 +2165,7 @@ static int update_relax_domain_level(struct cpuset *cs, s64 val)
* @cs: the cpuset in which each task's spread flags needs to be changed * @cs: the cpuset in which each task's spread flags needs to be changed
* *
* Iterate through each task of @cs updating its spread flags. As this * Iterate through each task of @cs updating its spread flags. As this
* function is called with cpuset_rwsem held, cpuset membership stays * function is called with cpuset_mutex held, cpuset membership stays
* stable. * stable.
*/ */
static void update_tasks_flags(struct cpuset *cs) static void update_tasks_flags(struct cpuset *cs)
@ -2184,7 +2185,7 @@ static void update_tasks_flags(struct cpuset *cs)
* cs: the cpuset to update * cs: the cpuset to update
* turning_on: whether the flag is being set or cleared * turning_on: whether the flag is being set or cleared
* *
* Call with cpuset_rwsem held. * Call with cpuset_mutex held.
*/ */
static int update_flag(cpuset_flagbits_t bit, struct cpuset *cs, static int update_flag(cpuset_flagbits_t bit, struct cpuset *cs,
@ -2234,7 +2235,7 @@ static int update_flag(cpuset_flagbits_t bit, struct cpuset *cs,
* @new_prs: new partition root state * @new_prs: new partition root state
* Return: 0 if successful, != 0 if error * Return: 0 if successful, != 0 if error
* *
* Call with cpuset_rwsem held. * Call with cpuset_mutex held.
*/ */
static int update_prstate(struct cpuset *cs, int new_prs) static int update_prstate(struct cpuset *cs, int new_prs)
{ {
@ -2472,7 +2473,7 @@ static int cpuset_can_attach_check(struct cpuset *cs)
return 0; return 0;
} }
/* Called by cgroups to determine if a cpuset is usable; cpuset_rwsem held */ /* Called by cgroups to determine if a cpuset is usable; cpuset_mutex held */
static int cpuset_can_attach(struct cgroup_taskset *tset) static int cpuset_can_attach(struct cgroup_taskset *tset)
{ {
struct cgroup_subsys_state *css; struct cgroup_subsys_state *css;
@ -2484,7 +2485,7 @@ static int cpuset_can_attach(struct cgroup_taskset *tset)
cpuset_attach_old_cs = task_cs(cgroup_taskset_first(tset, &css)); cpuset_attach_old_cs = task_cs(cgroup_taskset_first(tset, &css));
cs = css_cs(css); cs = css_cs(css);
percpu_down_write(&cpuset_rwsem); mutex_lock(&cpuset_mutex);
/* Check to see if task is allowed in the cpuset */ /* Check to see if task is allowed in the cpuset */
ret = cpuset_can_attach_check(cs); ret = cpuset_can_attach_check(cs);
@ -2506,7 +2507,7 @@ static int cpuset_can_attach(struct cgroup_taskset *tset)
*/ */
cs->attach_in_progress++; cs->attach_in_progress++;
out_unlock: out_unlock:
percpu_up_write(&cpuset_rwsem); mutex_unlock(&cpuset_mutex);
return ret; return ret;
} }
@ -2518,15 +2519,15 @@ static void cpuset_cancel_attach(struct cgroup_taskset *tset)
cgroup_taskset_first(tset, &css); cgroup_taskset_first(tset, &css);
cs = css_cs(css); cs = css_cs(css);
percpu_down_write(&cpuset_rwsem); mutex_lock(&cpuset_mutex);
cs->attach_in_progress--; cs->attach_in_progress--;
if (!cs->attach_in_progress) if (!cs->attach_in_progress)
wake_up(&cpuset_attach_wq); wake_up(&cpuset_attach_wq);
percpu_up_write(&cpuset_rwsem); mutex_unlock(&cpuset_mutex);
} }
/* /*
* Protected by cpuset_rwsem. cpus_attach is used only by cpuset_attach_task() * Protected by cpuset_mutex. cpus_attach is used only by cpuset_attach_task()
* but we can't allocate it dynamically there. Define it global and * but we can't allocate it dynamically there. Define it global and
* allocate from cpuset_init(). * allocate from cpuset_init().
*/ */
@ -2535,7 +2536,7 @@ static nodemask_t cpuset_attach_nodemask_to;
static void cpuset_attach_task(struct cpuset *cs, struct task_struct *task) static void cpuset_attach_task(struct cpuset *cs, struct task_struct *task)
{ {
percpu_rwsem_assert_held(&cpuset_rwsem); lockdep_assert_held(&cpuset_mutex);
if (cs != &top_cpuset) if (cs != &top_cpuset)
guarantee_online_cpus(task, cpus_attach); guarantee_online_cpus(task, cpus_attach);
@ -2565,7 +2566,7 @@ static void cpuset_attach(struct cgroup_taskset *tset)
cs = css_cs(css); cs = css_cs(css);
lockdep_assert_cpus_held(); /* see cgroup_attach_lock() */ lockdep_assert_cpus_held(); /* see cgroup_attach_lock() */
percpu_down_write(&cpuset_rwsem); mutex_lock(&cpuset_mutex);
cpus_updated = !cpumask_equal(cs->effective_cpus, cpus_updated = !cpumask_equal(cs->effective_cpus,
oldcs->effective_cpus); oldcs->effective_cpus);
mems_updated = !nodes_equal(cs->effective_mems, oldcs->effective_mems); mems_updated = !nodes_equal(cs->effective_mems, oldcs->effective_mems);
@ -2626,7 +2627,7 @@ static void cpuset_attach(struct cgroup_taskset *tset)
if (!cs->attach_in_progress) if (!cs->attach_in_progress)
wake_up(&cpuset_attach_wq); wake_up(&cpuset_attach_wq);
percpu_up_write(&cpuset_rwsem); mutex_unlock(&cpuset_mutex);
} }
/* The various types of files and directories in a cpuset file system */ /* The various types of files and directories in a cpuset file system */
@ -2658,7 +2659,7 @@ static int cpuset_write_u64(struct cgroup_subsys_state *css, struct cftype *cft,
int retval = 0; int retval = 0;
cpus_read_lock(); cpus_read_lock();
percpu_down_write(&cpuset_rwsem); mutex_lock(&cpuset_mutex);
if (!is_cpuset_online(cs)) { if (!is_cpuset_online(cs)) {
retval = -ENODEV; retval = -ENODEV;
goto out_unlock; goto out_unlock;
@ -2694,7 +2695,7 @@ static int cpuset_write_u64(struct cgroup_subsys_state *css, struct cftype *cft,
break; break;
} }
out_unlock: out_unlock:
percpu_up_write(&cpuset_rwsem); mutex_unlock(&cpuset_mutex);
cpus_read_unlock(); cpus_read_unlock();
return retval; return retval;
} }
@ -2707,7 +2708,7 @@ static int cpuset_write_s64(struct cgroup_subsys_state *css, struct cftype *cft,
int retval = -ENODEV; int retval = -ENODEV;
cpus_read_lock(); cpus_read_lock();
percpu_down_write(&cpuset_rwsem); mutex_lock(&cpuset_mutex);
if (!is_cpuset_online(cs)) if (!is_cpuset_online(cs))
goto out_unlock; goto out_unlock;
@ -2720,7 +2721,7 @@ static int cpuset_write_s64(struct cgroup_subsys_state *css, struct cftype *cft,
break; break;
} }
out_unlock: out_unlock:
percpu_up_write(&cpuset_rwsem); mutex_unlock(&cpuset_mutex);
cpus_read_unlock(); cpus_read_unlock();
return retval; return retval;
} }
@ -2753,7 +2754,7 @@ static ssize_t cpuset_write_resmask(struct kernfs_open_file *of,
* operation like this one can lead to a deadlock through kernfs * operation like this one can lead to a deadlock through kernfs
* active_ref protection. Let's break the protection. Losing the * active_ref protection. Let's break the protection. Losing the
* protection is okay as we check whether @cs is online after * protection is okay as we check whether @cs is online after
* grabbing cpuset_rwsem anyway. This only happens on the legacy * grabbing cpuset_mutex anyway. This only happens on the legacy
* hierarchies. * hierarchies.
*/ */
css_get(&cs->css); css_get(&cs->css);
@ -2761,7 +2762,7 @@ static ssize_t cpuset_write_resmask(struct kernfs_open_file *of,
flush_work(&cpuset_hotplug_work); flush_work(&cpuset_hotplug_work);
cpus_read_lock(); cpus_read_lock();
percpu_down_write(&cpuset_rwsem); mutex_lock(&cpuset_mutex);
if (!is_cpuset_online(cs)) if (!is_cpuset_online(cs))
goto out_unlock; goto out_unlock;
@ -2785,7 +2786,7 @@ static ssize_t cpuset_write_resmask(struct kernfs_open_file *of,
free_cpuset(trialcs); free_cpuset(trialcs);
out_unlock: out_unlock:
percpu_up_write(&cpuset_rwsem); mutex_unlock(&cpuset_mutex);
cpus_read_unlock(); cpus_read_unlock();
kernfs_unbreak_active_protection(of->kn); kernfs_unbreak_active_protection(of->kn);
css_put(&cs->css); css_put(&cs->css);
@ -2933,13 +2934,13 @@ static ssize_t sched_partition_write(struct kernfs_open_file *of, char *buf,
css_get(&cs->css); css_get(&cs->css);
cpus_read_lock(); cpus_read_lock();
percpu_down_write(&cpuset_rwsem); mutex_lock(&cpuset_mutex);
if (!is_cpuset_online(cs)) if (!is_cpuset_online(cs))
goto out_unlock; goto out_unlock;
retval = update_prstate(cs, val); retval = update_prstate(cs, val);
out_unlock: out_unlock:
percpu_up_write(&cpuset_rwsem); mutex_unlock(&cpuset_mutex);
cpus_read_unlock(); cpus_read_unlock();
css_put(&cs->css); css_put(&cs->css);
return retval ?: nbytes; return retval ?: nbytes;
@ -3156,7 +3157,7 @@ static int cpuset_css_online(struct cgroup_subsys_state *css)
return 0; return 0;
cpus_read_lock(); cpus_read_lock();
percpu_down_write(&cpuset_rwsem); mutex_lock(&cpuset_mutex);
set_bit(CS_ONLINE, &cs->flags); set_bit(CS_ONLINE, &cs->flags);
if (is_spread_page(parent)) if (is_spread_page(parent))
@ -3207,7 +3208,7 @@ static int cpuset_css_online(struct cgroup_subsys_state *css)
cpumask_copy(cs->effective_cpus, parent->cpus_allowed); cpumask_copy(cs->effective_cpus, parent->cpus_allowed);
spin_unlock_irq(&callback_lock); spin_unlock_irq(&callback_lock);
out_unlock: out_unlock:
percpu_up_write(&cpuset_rwsem); mutex_unlock(&cpuset_mutex);
cpus_read_unlock(); cpus_read_unlock();
return 0; return 0;
} }
@ -3228,7 +3229,7 @@ static void cpuset_css_offline(struct cgroup_subsys_state *css)
struct cpuset *cs = css_cs(css); struct cpuset *cs = css_cs(css);
cpus_read_lock(); cpus_read_lock();
percpu_down_write(&cpuset_rwsem); mutex_lock(&cpuset_mutex);
if (is_partition_valid(cs)) if (is_partition_valid(cs))
update_prstate(cs, 0); update_prstate(cs, 0);
@ -3247,7 +3248,7 @@ static void cpuset_css_offline(struct cgroup_subsys_state *css)
cpuset_dec(); cpuset_dec();
clear_bit(CS_ONLINE, &cs->flags); clear_bit(CS_ONLINE, &cs->flags);
percpu_up_write(&cpuset_rwsem); mutex_unlock(&cpuset_mutex);
cpus_read_unlock(); cpus_read_unlock();
} }
@ -3260,7 +3261,7 @@ static void cpuset_css_free(struct cgroup_subsys_state *css)
static void cpuset_bind(struct cgroup_subsys_state *root_css) static void cpuset_bind(struct cgroup_subsys_state *root_css)
{ {
percpu_down_write(&cpuset_rwsem); mutex_lock(&cpuset_mutex);
spin_lock_irq(&callback_lock); spin_lock_irq(&callback_lock);
if (is_in_v2_mode()) { if (is_in_v2_mode()) {
@ -3273,7 +3274,7 @@ static void cpuset_bind(struct cgroup_subsys_state *root_css)
} }
spin_unlock_irq(&callback_lock); spin_unlock_irq(&callback_lock);
percpu_up_write(&cpuset_rwsem); mutex_unlock(&cpuset_mutex);
} }
/* /*
@ -3294,7 +3295,7 @@ static int cpuset_can_fork(struct task_struct *task, struct css_set *cset)
return 0; return 0;
lockdep_assert_held(&cgroup_mutex); lockdep_assert_held(&cgroup_mutex);
percpu_down_write(&cpuset_rwsem); mutex_lock(&cpuset_mutex);
/* Check to see if task is allowed in the cpuset */ /* Check to see if task is allowed in the cpuset */
ret = cpuset_can_attach_check(cs); ret = cpuset_can_attach_check(cs);
@ -3315,7 +3316,7 @@ static int cpuset_can_fork(struct task_struct *task, struct css_set *cset)
*/ */
cs->attach_in_progress++; cs->attach_in_progress++;
out_unlock: out_unlock:
percpu_up_write(&cpuset_rwsem); mutex_unlock(&cpuset_mutex);
return ret; return ret;
} }
@ -3331,11 +3332,11 @@ static void cpuset_cancel_fork(struct task_struct *task, struct css_set *cset)
if (same_cs) if (same_cs)
return; return;
percpu_down_write(&cpuset_rwsem); mutex_lock(&cpuset_mutex);
cs->attach_in_progress--; cs->attach_in_progress--;
if (!cs->attach_in_progress) if (!cs->attach_in_progress)
wake_up(&cpuset_attach_wq); wake_up(&cpuset_attach_wq);
percpu_up_write(&cpuset_rwsem); mutex_unlock(&cpuset_mutex);
} }
/* /*
@ -3363,7 +3364,7 @@ static void cpuset_fork(struct task_struct *task)
} }
/* CLONE_INTO_CGROUP */ /* CLONE_INTO_CGROUP */
percpu_down_write(&cpuset_rwsem); mutex_lock(&cpuset_mutex);
guarantee_online_mems(cs, &cpuset_attach_nodemask_to); guarantee_online_mems(cs, &cpuset_attach_nodemask_to);
cpuset_attach_task(cs, task); cpuset_attach_task(cs, task);
@ -3371,7 +3372,7 @@ static void cpuset_fork(struct task_struct *task)
if (!cs->attach_in_progress) if (!cs->attach_in_progress)
wake_up(&cpuset_attach_wq); wake_up(&cpuset_attach_wq);
percpu_up_write(&cpuset_rwsem); mutex_unlock(&cpuset_mutex);
} }
struct cgroup_subsys cpuset_cgrp_subsys = { struct cgroup_subsys cpuset_cgrp_subsys = {
@ -3472,7 +3473,7 @@ hotplug_update_tasks_legacy(struct cpuset *cs,
is_empty = cpumask_empty(cs->cpus_allowed) || is_empty = cpumask_empty(cs->cpus_allowed) ||
nodes_empty(cs->mems_allowed); nodes_empty(cs->mems_allowed);
percpu_up_write(&cpuset_rwsem); mutex_unlock(&cpuset_mutex);
/* /*
* Move tasks to the nearest ancestor with execution resources, * Move tasks to the nearest ancestor with execution resources,
@ -3482,7 +3483,7 @@ hotplug_update_tasks_legacy(struct cpuset *cs,
if (is_empty) if (is_empty)
remove_tasks_in_empty_cpuset(cs); remove_tasks_in_empty_cpuset(cs);
percpu_down_write(&cpuset_rwsem); mutex_lock(&cpuset_mutex);
} }
static void static void
@ -3533,14 +3534,14 @@ static void cpuset_hotplug_update_tasks(struct cpuset *cs, struct tmpmasks *tmp)
retry: retry:
wait_event(cpuset_attach_wq, cs->attach_in_progress == 0); wait_event(cpuset_attach_wq, cs->attach_in_progress == 0);
percpu_down_write(&cpuset_rwsem); mutex_lock(&cpuset_mutex);
/* /*
* We have raced with task attaching. We wait until attaching * We have raced with task attaching. We wait until attaching
* is finished, so we won't attach a task to an empty cpuset. * is finished, so we won't attach a task to an empty cpuset.
*/ */
if (cs->attach_in_progress) { if (cs->attach_in_progress) {
percpu_up_write(&cpuset_rwsem); mutex_unlock(&cpuset_mutex);
goto retry; goto retry;
} }
@ -3637,7 +3638,7 @@ static void cpuset_hotplug_update_tasks(struct cpuset *cs, struct tmpmasks *tmp)
cpus_updated, mems_updated); cpus_updated, mems_updated);
unlock: unlock:
percpu_up_write(&cpuset_rwsem); mutex_unlock(&cpuset_mutex);
} }
/** /**
@ -3667,7 +3668,7 @@ static void cpuset_hotplug_workfn(struct work_struct *work)
if (on_dfl && !alloc_cpumasks(NULL, &tmp)) if (on_dfl && !alloc_cpumasks(NULL, &tmp))
ptmp = &tmp; ptmp = &tmp;
percpu_down_write(&cpuset_rwsem); mutex_lock(&cpuset_mutex);
/* fetch the available cpus/mems and find out which changed how */ /* fetch the available cpus/mems and find out which changed how */
cpumask_copy(&new_cpus, cpu_active_mask); cpumask_copy(&new_cpus, cpu_active_mask);
@ -3724,7 +3725,7 @@ static void cpuset_hotplug_workfn(struct work_struct *work)
update_tasks_nodemask(&top_cpuset); update_tasks_nodemask(&top_cpuset);
} }
percpu_up_write(&cpuset_rwsem); mutex_unlock(&cpuset_mutex);
/* if cpus or mems changed, we need to propagate to descendants */ /* if cpus or mems changed, we need to propagate to descendants */
if (cpus_updated || mems_updated) { if (cpus_updated || mems_updated) {
@ -4155,7 +4156,7 @@ void __cpuset_memory_pressure_bump(void)
* - Used for /proc/<pid>/cpuset. * - Used for /proc/<pid>/cpuset.
* - No need to task_lock(tsk) on this tsk->cpuset reference, as it * - No need to task_lock(tsk) on this tsk->cpuset reference, as it
* doesn't really matter if tsk->cpuset changes after we read it, * doesn't really matter if tsk->cpuset changes after we read it,
* and we take cpuset_rwsem, keeping cpuset_attach() from changing it * and we take cpuset_mutex, keeping cpuset_attach() from changing it
* anyway. * anyway.
*/ */
int proc_cpuset_show(struct seq_file *m, struct pid_namespace *ns, int proc_cpuset_show(struct seq_file *m, struct pid_namespace *ns,

22
kernel/sched/core.c
View File

@ -7590,6 +7590,7 @@ static int __sched_setscheduler(struct task_struct *p,
int reset_on_fork; int reset_on_fork;
int queue_flags = DEQUEUE_SAVE | DEQUEUE_MOVE | DEQUEUE_NOCLOCK; int queue_flags = DEQUEUE_SAVE | DEQUEUE_MOVE | DEQUEUE_NOCLOCK;
struct rq *rq; struct rq *rq;
bool cpuset_locked = false;
/* The pi code expects interrupts enabled */ /* The pi code expects interrupts enabled */
BUG_ON(pi && in_interrupt()); BUG_ON(pi && in_interrupt());
@ -7639,8 +7640,14 @@ static int __sched_setscheduler(struct task_struct *p,
return retval; return retval;
} }
if (pi) /*
cpuset_read_lock(); * SCHED_DEADLINE bandwidth accounting relies on stable cpusets
* information.
*/
if (dl_policy(policy) || dl_policy(p->policy)) {
cpuset_locked = true;
cpuset_lock();
}
/* /*
* Make sure no PI-waiters arrive (or leave) while we are * Make sure no PI-waiters arrive (or leave) while we are
@ -7716,8 +7723,8 @@ static int __sched_setscheduler(struct task_struct *p,
if (unlikely(oldpolicy != -1 && oldpolicy != p->policy)) { if (unlikely(oldpolicy != -1 && oldpolicy != p->policy)) {
policy = oldpolicy = -1; policy = oldpolicy = -1;
task_rq_unlock(rq, p, &rf); task_rq_unlock(rq, p, &rf);
if (pi) if (cpuset_locked)
cpuset_read_unlock(); cpuset_unlock();
goto recheck; goto recheck;
} }
@ -7784,7 +7791,8 @@ static int __sched_setscheduler(struct task_struct *p,
task_rq_unlock(rq, p, &rf); task_rq_unlock(rq, p, &rf);
if (pi) { if (pi) {
cpuset_read_unlock(); if (cpuset_locked)
cpuset_unlock();
rt_mutex_adjust_pi(p); rt_mutex_adjust_pi(p);
} }
@ -7796,8 +7804,8 @@ static int __sched_setscheduler(struct task_struct *p,
unlock: unlock:
task_rq_unlock(rq, p, &rf); task_rq_unlock(rq, p, &rf);
if (pi) if (cpuset_locked)
cpuset_read_unlock(); cpuset_unlock();
return retval; return retval;
} }