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Message-ID: <623f214b-8b9a-f967-7a3d-ca9c06151267@codeaurora.org>
Date: Mon, 4 Dec 2017 10:44:49 +0530
From: Prateek Sood <prsood@...eaurora.org>
To: tj@...nel.org, avagin@...il.com, mingo@...nel.org,
peterz@...radead.org
Cc: linux-kernel@...r.kernel.org, cgroups@...r.kernel.org,
sramana@...eaurora.org
Subject: Re: [PATCH] cgroup/cpuset: fix circular locking dependency
On 11/28/2017 05:05 PM, Prateek Sood wrote:
> CPU1
> cpus_read_lock+0x3e/0x80
> static_key_slow_inc+0xe/0xa0
> cpuset_css_online+0x62/0x330
> online_css+0x26/0x80
> cgroup_apply_control_enable+0x266/0x3d0
> cgroup_mkdir+0x37d/0x4f0
> kernfs_iop_mkdir+0x53/0x80
> vfs_mkdir+0x10e/0x1a0
> SyS_mkdirat+0xb3/0xe0
> entry_SYSCALL_64_fastpath+0x23/0x9a
>
> CPU0
> lock_acquire+0xec/0x1e0
> __mutex_lock+0x89/0x920
> cpuset_write_resmask+0x61/0x1100
> cgroup_file_write+0x7b/0x200
> kernfs_fop_write+0x112/0x1a0
> __vfs_write+0x23/0x150
> vfs_write+0xc8/0x1c0
> SyS_write+0x45/0xa0
> entry_SYSCALL_64_fastpath+0x23/0x9a
>
> CPU0 CPU1
> ---- ----
> lock(cpu_hotplug_lock.rw_sem);
> lock(cpuset_mutex);
> lock(cpu_hotplug_lock.rw_sem);
> lock(cpuset_mutex);
>
> Change locking order of cpu_hotplug_lock.rw_sem and
> cpuset_mutex in cpuset_css_online(). Use _cpuslocked()
> version for static_branch_inc/static_branch_dec in
> cpuset_inc()/cpuset_dec().
>
> Signed-off-by: Prateek Sood <prsood@...eaurora.org>
> ---
> include/linux/cpuset.h | 8 ++++----
> include/linux/jump_label.h | 10 ++++++++--
> kernel/cgroup/cpuset.c | 4 ++--
> kernel/jump_label.c | 13 +++++++++++++
> 4 files changed, 27 insertions(+), 8 deletions(-)
>
> diff --git a/include/linux/cpuset.h b/include/linux/cpuset.h
> index 2ab910f..5aadc25 100644
> --- a/include/linux/cpuset.h
> +++ b/include/linux/cpuset.h
> @@ -40,14 +40,14 @@ static inline bool cpusets_enabled(void)
>
> static inline void cpuset_inc(void)
> {
> - static_branch_inc(&cpusets_pre_enable_key);
> - static_branch_inc(&cpusets_enabled_key);
> + static_branch_inc_cpuslocked(&cpusets_pre_enable_key);
> + static_branch_inc_cpuslocked(&cpusets_enabled_key);
> }
>
> static inline void cpuset_dec(void)
> {
> - static_branch_dec(&cpusets_enabled_key);
> - static_branch_dec(&cpusets_pre_enable_key);
> + static_branch_dec_cpuslocked(&cpusets_enabled_key);
> + static_branch_dec_cpuslocked(&cpusets_pre_enable_key);
> }
>
> extern int cpuset_init(void);
> diff --git a/include/linux/jump_label.h b/include/linux/jump_label.h
> index c7b368c..890e21c 100644
> --- a/include/linux/jump_label.h
> +++ b/include/linux/jump_label.h
> @@ -160,6 +160,8 @@ extern void arch_jump_label_transform_static(struct jump_entry *entry,
> extern int jump_label_text_reserved(void *start, void *end);
> extern void static_key_slow_inc(struct static_key *key);
> extern void static_key_slow_dec(struct static_key *key);
> +extern void static_key_slow_incr_cpuslocked(struct static_key *key);
> +extern void static_key_slow_decr_cpuslocked(struct static_key *key);
> extern void jump_label_apply_nops(struct module *mod);
> extern int static_key_count(struct static_key *key);
> extern void static_key_enable(struct static_key *key);
> @@ -259,6 +261,8 @@ static inline void static_key_disable(struct static_key *key)
>
> #define static_key_enable_cpuslocked(k) static_key_enable((k))
> #define static_key_disable_cpuslocked(k) static_key_disable((k))
> +#define static_key_slow_incr_cpuslocked(k) static_key_slow_inc((k))
> +#define static_key_slow_decr_cpuslocked(k) static_key_slow_dec((k))
>
> #define STATIC_KEY_INIT_TRUE { .enabled = ATOMIC_INIT(1) }
> #define STATIC_KEY_INIT_FALSE { .enabled = ATOMIC_INIT(0) }
> @@ -414,8 +418,10 @@ struct static_key_false {
> * Advanced usage; refcount, branch is enabled when: count != 0
> */
>
> -#define static_branch_inc(x) static_key_slow_inc(&(x)->key)
> -#define static_branch_dec(x) static_key_slow_dec(&(x)->key)
> +#define static_branch_inc(x) static_key_slow_inc(&(x)->key)
> +#define static_branch_dec(x) static_key_slow_dec(&(x)->key)
> +#define static_branch_inc_cpuslocked(x) static_key_slow_incr_cpuslocked(&(x)->key)
> +#define static_branch_dec_cpuslocked(x) static_key_slow_decr_cpuslocked(&(x)->key)
>
> /*
> * Normal usage; boolean enable/disable.
> diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
> index 227bc25..4ad8bae 100644
> --- a/kernel/cgroup/cpuset.c
> +++ b/kernel/cgroup/cpuset.c
> @@ -1985,7 +1985,7 @@ static int cpuset_css_online(struct cgroup_subsys_state *css)
> if (!parent)
> return 0;
>
> - mutex_lock(&cpuset_mutex);
> + cpuset_sched_change_begin();
>
> set_bit(CS_ONLINE, &cs->flags);
> if (is_spread_page(parent))
> @@ -2034,7 +2034,7 @@ static int cpuset_css_online(struct cgroup_subsys_state *css)
> cpumask_copy(cs->effective_cpus, parent->cpus_allowed);
> spin_unlock_irq(&callback_lock);
> out_unlock:
> - mutex_unlock(&cpuset_mutex);
> + cpuset_sched_change_end();
> return 0;
> }
>
> diff --git a/kernel/jump_label.c b/kernel/jump_label.c
> index 8594d24..dde0eaa 100644
> --- a/kernel/jump_label.c
> +++ b/kernel/jump_label.c
> @@ -126,6 +126,12 @@ void static_key_slow_inc(struct static_key *key)
> }
> EXPORT_SYMBOL_GPL(static_key_slow_inc);
>
> +void static_key_slow_incr_cpuslocked(struct static_key *key)
> +{
> + static_key_slow_inc_cpuslocked(key);
> +}
> +EXPORT_SYMBOL_GPL(static_key_slow_incr_cpuslocked);
> +
> void static_key_enable_cpuslocked(struct static_key *key)
> {
> STATIC_KEY_CHECK_USE(key);
> @@ -229,6 +235,13 @@ void static_key_slow_dec(struct static_key *key)
> }
> EXPORT_SYMBOL_GPL(static_key_slow_dec);
>
> +void static_key_slow_decr_cpuslocked(struct static_key *key)
> +{
> + STATIC_KEY_CHECK_USE(key);
> + static_key_slow_dec_cpuslocked(key, 0, NULL);
> +}
> +EXPORT_SYMBOL_GPL(static_key_slow_decr_cpuslocked);
> +
> void static_key_slow_dec_deferred(struct static_key_deferred *key)
> {
> STATIC_KEY_CHECK_USE(key);
>
TJ,
Any feedback/suggestion for this patch?
--
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