From: Michal Hocko <mhocko@kernel.org> To: Thomas Gleixner <tglx@linutronix.de> Cc: LKML <linux-kernel@vger.kernel.org>, linux-mm@kvack.org, Andrey Ryabinin <aryabinin@virtuozzo.com>, Andrew Morton <akpm@linux-foundation.org>, Vlastimil Babka <vbabka@suse.cz>, Vladimir Davydov <vdavydov.dev@gmail.com>, Peter Zijlstra <peterz@infradead.org> Subject: Re: [patch V2 2/2] mm/memory-hotplug: Switch locking to a percpu rwsem Date: Tue, 4 Jul 2017 12:59:15 +0200 [thread overview] Message-ID: <20170704105915.GL14722@dhcp22.suse.cz> (raw) In-Reply-To: <20170704093421.506836322@linutronix.de> On Tue 04-07-17 11:32:34, Thomas Gleixner wrote: > Andrey reported a potential deadlock with the memory hotplug lock and the > cpu hotplug lock. > > The reason is that memory hotplug takes the memory hotplug lock and then > calls stop_machine() which calls get_online_cpus(). That's the reverse lock > order to get_online_cpus(); get_online_mems(); in mm/slub_common.c > > The problem has been there forever. The reason why this was never reported > is that the cpu hotplug locking had this homebrewn recursive reader writer > semaphore construct which due to the recursion evaded the full lock dep > coverage. The memory hotplug code copied that construct verbatim and > therefor has similar issues. > > Three steps to fix this: > > 1) Convert the memory hotplug locking to a per cpu rwsem so the potential > issues get reported proper by lockdep. > > 2) Lock the online cpus in mem_hotplug_begin() before taking the memory > hotplug rwsem and use stop_machine_cpuslocked() in the page_alloc code > and use to avoid recursive locking. > > 3) The cpu hotpluck locking in #2 causes a recursive locking of the cpu > hotplug lock via __offline_pages() -> lru_add_drain_all(). Solve this by > invoking lru_add_drain_all_cpuslocked() instead. > > Reported-by: Andrey Ryabinin <aryabinin@virtuozzo.com> > Signed-off-by: Thomas Gleixner <tglx@linutronix.de> > Cc: Michal Hocko <mhocko@kernel.org> > Cc: linux-mm@kvack.org > Cc: Andrew Morton <akpm@linux-foundation.org> > Cc: Vlastimil Babka <vbabka@suse.cz> > Cc: Vladimir Davydov <vdavydov.dev@gmail.com> Acked-by: Michal Hocko <mhocko@suse.com> > --- > mm/memory_hotplug.c | 89 ++++++++-------------------------------------------- > mm/page_alloc.c | 2 - > 2 files changed, 16 insertions(+), 75 deletions(-) > > --- a/mm/memory_hotplug.c > +++ b/mm/memory_hotplug.c > @@ -52,32 +52,17 @@ static void generic_online_page(struct p > static online_page_callback_t online_page_callback = generic_online_page; > static DEFINE_MUTEX(online_page_callback_lock); > > -/* The same as the cpu_hotplug lock, but for memory hotplug. */ > -static struct { > - struct task_struct *active_writer; > - struct mutex lock; /* Synchronizes accesses to refcount, */ > - /* > - * Also blocks the new readers during > - * an ongoing mem hotplug operation. > - */ > - int refcount; > +DEFINE_STATIC_PERCPU_RWSEM(mem_hotplug_lock); > > -#ifdef CONFIG_DEBUG_LOCK_ALLOC > - struct lockdep_map dep_map; > -#endif > -} mem_hotplug = { > - .active_writer = NULL, > - .lock = __MUTEX_INITIALIZER(mem_hotplug.lock), > - .refcount = 0, > -#ifdef CONFIG_DEBUG_LOCK_ALLOC > - .dep_map = {.name = "mem_hotplug.lock" }, > -#endif > -}; > +void get_online_mems(void) > +{ > + percpu_down_read(&mem_hotplug_lock); > +} > > -/* Lockdep annotations for get/put_online_mems() and mem_hotplug_begin/end() */ > -#define memhp_lock_acquire_read() lock_map_acquire_read(&mem_hotplug.dep_map) > -#define memhp_lock_acquire() lock_map_acquire(&mem_hotplug.dep_map) > -#define memhp_lock_release() lock_map_release(&mem_hotplug.dep_map) > +void put_online_mems(void) > +{ > + percpu_up_read(&mem_hotplug_lock); > +} > > #ifndef CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE > bool memhp_auto_online; > @@ -97,60 +82,16 @@ static int __init setup_memhp_default_st > } > __setup("memhp_default_state=", setup_memhp_default_state); > > -void get_online_mems(void) > -{ > - might_sleep(); > - if (mem_hotplug.active_writer == current) > - return; > - memhp_lock_acquire_read(); > - mutex_lock(&mem_hotplug.lock); > - mem_hotplug.refcount++; > - mutex_unlock(&mem_hotplug.lock); > - > -} > - > -void put_online_mems(void) > -{ > - if (mem_hotplug.active_writer == current) > - return; > - mutex_lock(&mem_hotplug.lock); > - > - if (WARN_ON(!mem_hotplug.refcount)) > - mem_hotplug.refcount++; /* try to fix things up */ > - > - if (!--mem_hotplug.refcount && unlikely(mem_hotplug.active_writer)) > - wake_up_process(mem_hotplug.active_writer); > - mutex_unlock(&mem_hotplug.lock); > - memhp_lock_release(); > - > -} > - > -/* Serializes write accesses to mem_hotplug.active_writer. */ > -static DEFINE_MUTEX(memory_add_remove_lock); > - > void mem_hotplug_begin(void) > { > - mutex_lock(&memory_add_remove_lock); > - > - mem_hotplug.active_writer = current; > - > - memhp_lock_acquire(); > - for (;;) { > - mutex_lock(&mem_hotplug.lock); > - if (likely(!mem_hotplug.refcount)) > - break; > - __set_current_state(TASK_UNINTERRUPTIBLE); > - mutex_unlock(&mem_hotplug.lock); > - schedule(); > - } > + cpus_read_lock(); > + percpu_down_write(&mem_hotplug_lock); > } > > void mem_hotplug_done(void) > { > - mem_hotplug.active_writer = NULL; > - mutex_unlock(&mem_hotplug.lock); > - memhp_lock_release(); > - mutex_unlock(&memory_add_remove_lock); > + percpu_up_write(&mem_hotplug_lock); > + cpus_read_unlock(); > } > > /* add this memory to iomem resource */ > @@ -1919,7 +1860,7 @@ static int __ref __offline_pages(unsigne > goto failed_removal; > ret = 0; > if (drain) { > - lru_add_drain_all(); > + lru_add_drain_all_cpuslocked(); > cond_resched(); > drain_all_pages(zone); > } > @@ -1940,7 +1881,7 @@ static int __ref __offline_pages(unsigne > } > } > /* drain all zone's lru pagevec, this is asynchronous... */ > - lru_add_drain_all(); > + lru_add_drain_all_cpuslocked(); > yield(); > /* drain pcp pages, this is synchronous. */ > drain_all_pages(zone); > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -5216,7 +5216,7 @@ void __ref build_all_zonelists(pg_data_t > #endif > /* we have to stop all cpus to guarantee there is no user > of zonelist */ > - stop_machine(__build_all_zonelists, pgdat, NULL); > + stop_machine_cpuslocked(__build_all_zonelists, pgdat, NULL); > /* cpuset refresh routine should be here */ > } > vm_total_pages = nr_free_pagecache_pages(); > -- Michal Hocko SUSE Labs
WARNING: multiple messages have this Message-ID (diff)
From: Michal Hocko <mhocko@kernel.org> To: Thomas Gleixner <tglx@linutronix.de> Cc: LKML <linux-kernel@vger.kernel.org>, linux-mm@kvack.org, Andrey Ryabinin <aryabinin@virtuozzo.com>, Andrew Morton <akpm@linux-foundation.org>, Vlastimil Babka <vbabka@suse.cz>, Vladimir Davydov <vdavydov.dev@gmail.com>, Peter Zijlstra <peterz@infradead.org> Subject: Re: [patch V2 2/2] mm/memory-hotplug: Switch locking to a percpu rwsem Date: Tue, 4 Jul 2017 12:59:15 +0200 [thread overview] Message-ID: <20170704105915.GL14722@dhcp22.suse.cz> (raw) In-Reply-To: <20170704093421.506836322@linutronix.de> On Tue 04-07-17 11:32:34, Thomas Gleixner wrote: > Andrey reported a potential deadlock with the memory hotplug lock and the > cpu hotplug lock. > > The reason is that memory hotplug takes the memory hotplug lock and then > calls stop_machine() which calls get_online_cpus(). That's the reverse lock > order to get_online_cpus(); get_online_mems(); in mm/slub_common.c > > The problem has been there forever. The reason why this was never reported > is that the cpu hotplug locking had this homebrewn recursive reader writer > semaphore construct which due to the recursion evaded the full lock dep > coverage. The memory hotplug code copied that construct verbatim and > therefor has similar issues. > > Three steps to fix this: > > 1) Convert the memory hotplug locking to a per cpu rwsem so the potential > issues get reported proper by lockdep. > > 2) Lock the online cpus in mem_hotplug_begin() before taking the memory > hotplug rwsem and use stop_machine_cpuslocked() in the page_alloc code > and use to avoid recursive locking. > > 3) The cpu hotpluck locking in #2 causes a recursive locking of the cpu > hotplug lock via __offline_pages() -> lru_add_drain_all(). Solve this by > invoking lru_add_drain_all_cpuslocked() instead. > > Reported-by: Andrey Ryabinin <aryabinin@virtuozzo.com> > Signed-off-by: Thomas Gleixner <tglx@linutronix.de> > Cc: Michal Hocko <mhocko@kernel.org> > Cc: linux-mm@kvack.org > Cc: Andrew Morton <akpm@linux-foundation.org> > Cc: Vlastimil Babka <vbabka@suse.cz> > Cc: Vladimir Davydov <vdavydov.dev@gmail.com> Acked-by: Michal Hocko <mhocko@suse.com> > --- > mm/memory_hotplug.c | 89 ++++++++-------------------------------------------- > mm/page_alloc.c | 2 - > 2 files changed, 16 insertions(+), 75 deletions(-) > > --- a/mm/memory_hotplug.c > +++ b/mm/memory_hotplug.c > @@ -52,32 +52,17 @@ static void generic_online_page(struct p > static online_page_callback_t online_page_callback = generic_online_page; > static DEFINE_MUTEX(online_page_callback_lock); > > -/* The same as the cpu_hotplug lock, but for memory hotplug. */ > -static struct { > - struct task_struct *active_writer; > - struct mutex lock; /* Synchronizes accesses to refcount, */ > - /* > - * Also blocks the new readers during > - * an ongoing mem hotplug operation. > - */ > - int refcount; > +DEFINE_STATIC_PERCPU_RWSEM(mem_hotplug_lock); > > -#ifdef CONFIG_DEBUG_LOCK_ALLOC > - struct lockdep_map dep_map; > -#endif > -} mem_hotplug = { > - .active_writer = NULL, > - .lock = __MUTEX_INITIALIZER(mem_hotplug.lock), > - .refcount = 0, > -#ifdef CONFIG_DEBUG_LOCK_ALLOC > - .dep_map = {.name = "mem_hotplug.lock" }, > -#endif > -}; > +void get_online_mems(void) > +{ > + percpu_down_read(&mem_hotplug_lock); > +} > > -/* Lockdep annotations for get/put_online_mems() and mem_hotplug_begin/end() */ > -#define memhp_lock_acquire_read() lock_map_acquire_read(&mem_hotplug.dep_map) > -#define memhp_lock_acquire() lock_map_acquire(&mem_hotplug.dep_map) > -#define memhp_lock_release() lock_map_release(&mem_hotplug.dep_map) > +void put_online_mems(void) > +{ > + percpu_up_read(&mem_hotplug_lock); > +} > > #ifndef CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE > bool memhp_auto_online; > @@ -97,60 +82,16 @@ static int __init setup_memhp_default_st > } > __setup("memhp_default_state=", setup_memhp_default_state); > > -void get_online_mems(void) > -{ > - might_sleep(); > - if (mem_hotplug.active_writer == current) > - return; > - memhp_lock_acquire_read(); > - mutex_lock(&mem_hotplug.lock); > - mem_hotplug.refcount++; > - mutex_unlock(&mem_hotplug.lock); > - > -} > - > -void put_online_mems(void) > -{ > - if (mem_hotplug.active_writer == current) > - return; > - mutex_lock(&mem_hotplug.lock); > - > - if (WARN_ON(!mem_hotplug.refcount)) > - mem_hotplug.refcount++; /* try to fix things up */ > - > - if (!--mem_hotplug.refcount && unlikely(mem_hotplug.active_writer)) > - wake_up_process(mem_hotplug.active_writer); > - mutex_unlock(&mem_hotplug.lock); > - memhp_lock_release(); > - > -} > - > -/* Serializes write accesses to mem_hotplug.active_writer. */ > -static DEFINE_MUTEX(memory_add_remove_lock); > - > void mem_hotplug_begin(void) > { > - mutex_lock(&memory_add_remove_lock); > - > - mem_hotplug.active_writer = current; > - > - memhp_lock_acquire(); > - for (;;) { > - mutex_lock(&mem_hotplug.lock); > - if (likely(!mem_hotplug.refcount)) > - break; > - __set_current_state(TASK_UNINTERRUPTIBLE); > - mutex_unlock(&mem_hotplug.lock); > - schedule(); > - } > + cpus_read_lock(); > + percpu_down_write(&mem_hotplug_lock); > } > > void mem_hotplug_done(void) > { > - mem_hotplug.active_writer = NULL; > - mutex_unlock(&mem_hotplug.lock); > - memhp_lock_release(); > - mutex_unlock(&memory_add_remove_lock); > + percpu_up_write(&mem_hotplug_lock); > + cpus_read_unlock(); > } > > /* add this memory to iomem resource */ > @@ -1919,7 +1860,7 @@ static int __ref __offline_pages(unsigne > goto failed_removal; > ret = 0; > if (drain) { > - lru_add_drain_all(); > + lru_add_drain_all_cpuslocked(); > cond_resched(); > drain_all_pages(zone); > } > @@ -1940,7 +1881,7 @@ static int __ref __offline_pages(unsigne > } > } > /* drain all zone's lru pagevec, this is asynchronous... */ > - lru_add_drain_all(); > + lru_add_drain_all_cpuslocked(); > yield(); > /* drain pcp pages, this is synchronous. */ > drain_all_pages(zone); > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -5216,7 +5216,7 @@ void __ref build_all_zonelists(pg_data_t > #endif > /* we have to stop all cpus to guarantee there is no user > of zonelist */ > - stop_machine(__build_all_zonelists, pgdat, NULL); > + stop_machine_cpuslocked(__build_all_zonelists, pgdat, NULL); > /* cpuset refresh routine should be here */ > } > vm_total_pages = nr_free_pagecache_pages(); > -- Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2017-07-04 10:59 UTC|newest] Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top 2017-07-04 9:32 [patch V2 0/2] mm/memory_hotplug: Cure potential deadlocks vs. cpu hotplug lock Thomas Gleixner 2017-07-04 9:32 ` Thomas Gleixner 2017-07-04 9:32 ` [patch V2 1/2] mm: swap: Provide lru_add_drain_all_cpuslocked() Thomas Gleixner 2017-07-04 9:32 ` Thomas Gleixner 2017-07-04 10:58 ` Michal Hocko 2017-07-04 10:58 ` Michal Hocko 2017-07-04 12:48 ` Thomas Gleixner 2017-07-04 12:48 ` Thomas Gleixner 2017-07-04 12:52 ` Michal Hocko 2017-07-04 12:52 ` Michal Hocko 2017-07-04 12:07 ` Vlastimil Babka 2017-07-04 12:07 ` Vlastimil Babka 2017-07-04 12:35 ` Thomas Gleixner 2017-07-04 12:35 ` Thomas Gleixner 2017-07-04 9:32 ` [patch V2 2/2] mm/memory-hotplug: Switch locking to a percpu rwsem Thomas Gleixner 2017-07-04 9:32 ` Thomas Gleixner 2017-07-04 10:59 ` Michal Hocko [this message] 2017-07-04 10:59 ` Michal Hocko 2017-07-04 12:10 ` Vlastimil Babka 2017-07-04 12:10 ` Vlastimil Babka 2017-07-04 12:49 ` Thomas Gleixner 2017-07-04 12:49 ` Thomas Gleixner 2017-07-04 15:01 ` Davidlohr Bueso 2017-07-04 15:01 ` Davidlohr Bueso 2017-07-04 15:22 ` Davidlohr Bueso 2017-07-04 15:22 ` Davidlohr Bueso 2017-07-04 15:32 ` Thomas Gleixner 2017-07-04 15:32 ` Thomas Gleixner 2017-07-04 15:42 ` Davidlohr Bueso 2017-07-04 15:42 ` Davidlohr Bueso 2017-07-05 21:53 ` [patch V2 0/2] mm/memory_hotplug: Cure potential deadlocks vs. cpu hotplug lock Andrew Morton 2017-07-05 21:53 ` Andrew Morton 2017-07-06 6:34 ` Thomas Gleixner 2017-07-06 6:34 ` Thomas Gleixner
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