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Thu, 1 Aug 2024 14:28:18 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id S7LpLoKbq2YAAwAAD6G6ig (envelope-from ); Thu, 01 Aug 2024 14:28:18 +0000 Message-ID: Date: Thu, 1 Aug 2024 16:28:18 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] rcu/kvfree: Add kvfree_rcu_barrier() API Content-Language: en-US To: "Uladzislau Rezki (Sony)" , "Paul E . McKenney" Cc: RCU , LKML , Neeraj upadhyay , Boqun Feng , Joel Fernandes , Frederic Weisbecker , Oleksiy Avramchenko References: <20240801111039.79656-1-urezki@gmail.com> From: Vlastimil Babka Autocrypt: addr=vbabka@suse.cz; keydata= xsFNBFZdmxYBEADsw/SiUSjB0dM+vSh95UkgcHjzEVBlby/Fg+g42O7LAEkCYXi/vvq31JTB KxRWDHX0R2tgpFDXHnzZcQywawu8eSq0LxzxFNYMvtB7sV1pxYwej2qx9B75qW2plBs+7+YB 87tMFA+u+L4Z5xAzIimfLD5EKC56kJ1CsXlM8S/LHcmdD9Ctkn3trYDNnat0eoAcfPIP2OZ+ 9oe9IF/R28zmh0ifLXyJQQz5ofdj4bPf8ecEW0rhcqHfTD8k4yK0xxt3xW+6Exqp9n9bydiy tcSAw/TahjW6yrA+6JhSBv1v2tIm+itQc073zjSX8OFL51qQVzRFr7H2UQG33lw2QrvHRXqD Ot7ViKam7v0Ho9wEWiQOOZlHItOOXFphWb2yq3nzrKe45oWoSgkxKb97MVsQ+q2SYjJRBBH4 8qKhphADYxkIP6yut/eaj9ImvRUZZRi0DTc8xfnvHGTjKbJzC2xpFcY0DQbZzuwsIZ8OPJCc LM4S7mT25NE5kUTG/TKQCk922vRdGVMoLA7dIQrgXnRXtyT61sg8PG4wcfOnuWf8577aXP1x 6mzw3/jh3F+oSBHb/GcLC7mvWreJifUL2gEdssGfXhGWBo6zLS3qhgtwjay0Jl+kza1lo+Cv BB2T79D4WGdDuVa4eOrQ02TxqGN7G0Biz5ZLRSFzQSQwLn8fbwARAQABzSBWbGFzdGltaWwg QmFia2EgPHZiYWJrYUBzdXNlLmN6PsLBlAQTAQoAPgIbAwULCQgHAwUVCgkICwUWAgMBAAIe AQIXgBYhBKlA1DSZLC6OmRA9UCJPp+fMgqZkBQJkBREIBQkRadznAAoJECJPp+fMgqZkNxIQ ALZRqwdUGzqL2aeSavbum/VF/+td+nZfuH0xeWiO2w8mG0+nPd5j9ujYeHcUP1edE7uQrjOC Gs9sm8+W1xYnbClMJTsXiAV88D2btFUdU1mCXURAL9wWZ8Jsmz5ZH2V6AUszvNezsS/VIT87 AmTtj31TLDGwdxaZTSYLwAOOOtyqafOEq+gJB30RxTRE3h3G1zpO7OM9K6ysLdAlwAGYWgJJ V4JqGsQ/lyEtxxFpUCjb5Pztp7cQxhlkil0oBYHkudiG8j1U3DG8iC6rnB4yJaLphKx57NuQ PIY0Bccg+r9gIQ4XeSK2PQhdXdy3UWBr913ZQ9AI2usid3s5vabo4iBvpJNFLgUmxFnr73SJ KsRh/2OBsg1XXF/wRQGBO9vRuJUAbnaIVcmGOUogdBVS9Sun/Sy4GNA++KtFZK95U7J417/J Hub2xV6Ehc7UGW6fIvIQmzJ3zaTEfuriU1P8ayfddrAgZb25JnOW7L1zdYL8rXiezOyYZ8Fm ZyXjzWdO0RpxcUEp6GsJr11Bc4F3aae9OZtwtLL/jxc7y6pUugB00PodgnQ6CMcfR/HjXlae h2VS3zl9+tQWHu6s1R58t5BuMS2FNA58wU/IazImc/ZQA+slDBfhRDGYlExjg19UXWe/gMcl De3P1kxYPgZdGE2eZpRLIbt+rYnqQKy8UxlszsBNBFsZNTUBCACfQfpSsWJZyi+SHoRdVyX5 J6rI7okc4+b571a7RXD5UhS9dlVRVVAtrU9ANSLqPTQKGVxHrqD39XSw8hxK61pw8p90pg4G /N3iuWEvyt+t0SxDDkClnGsDyRhlUyEWYFEoBrrCizbmahOUwqkJbNMfzj5Y7n7OIJOxNRkB IBOjPdF26dMP69BwePQao1M8Acrrex9sAHYjQGyVmReRjVEtv9iG4DoTsnIR3amKVk6si4Ea X/mrapJqSCcBUVYUFH8M7bsm4CSxier5ofy8jTEa/CfvkqpKThTMCQPNZKY7hke5qEq1CBk2 wxhX48ZrJEFf1v3NuV3OimgsF2odzieNABEBAAHCwXwEGAEKACYCGwwWIQSpQNQ0mSwujpkQ PVAiT6fnzIKmZAUCZAUSmwUJDK5EZgAKCRAiT6fnzIKmZOJGEACOKABgo9wJXsbWhGWYO7mD 8R8mUyJHqbvaz+yTLnvRwfe/VwafFfDMx5GYVYzMY9TWpA8psFTKTUIIQmx2scYsRBUwm5VI EurRWKqENcDRjyo+ol59j0FViYysjQQeobXBDDE31t5SBg++veI6tXfpco/UiKEsDswL1WAr tEAZaruo7254TyH+gydURl2wJuzo/aZ7Y7PpqaODbYv727Dvm5eX64HCyyAH0s6sOCyGF5/p eIhrOn24oBf67KtdAN3H9JoFNUVTYJc1VJU3R1JtVdgwEdr+NEciEfYl0O19VpLE/PZxP4wX PWnhf5WjdoNI1Xec+RcJ5p/pSel0jnvBX8L2cmniYnmI883NhtGZsEWj++wyKiS4NranDFlA HdDM3b4lUth1pTtABKQ1YuTvehj7EfoWD3bv9kuGZGPrAeFNiHPdOT7DaXKeHpW9homgtBxj 8aX/UkSvEGJKUEbFL9cVa5tzyialGkSiZJNkWgeHe+jEcfRT6pJZOJidSCdzvJpbdJmm+eED w9XOLH1IIWh7RURU7G1iOfEfmImFeC3cbbS73LQEFGe1urxvIH5K/7vX+FkNcr9ujwWuPE9b 1C2o4i/yZPLXIVy387EjA6GZMqvQUFuSTs/GeBcv0NjIQi8867H3uLjz+mQy63fAitsDwLmR EP+ylKVEKb0Q2A== In-Reply-To: <20240801111039.79656-1-urezki@gmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Spam-Level: X-Spamd-Result: default: False [0.41 / 50.00]; SUSPICIOUS_RECIPS(1.50)[]; NEURAL_HAM_LONG(-1.00)[-1.000]; MIME_GOOD(-0.10)[text/plain]; XM_UA_NO_VERSION(0.01)[]; MID_RHS_MATCH_FROM(0.00)[]; FREEMAIL_TO(0.00)[gmail.com,kernel.org]; ARC_NA(0.00)[]; RCVD_TLS_ALL(0.00)[]; RCPT_COUNT_SEVEN(0.00)[9]; TAGGED_RCPT(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; TO_DN_ALL(0.00)[]; FREEMAIL_ENVRCPT(0.00)[gmail.com]; DKIM_SIGNED(0.00)[suse.cz:s=susede2_rsa,suse.cz:s=susede2_ed25519]; FROM_HAS_DN(0.00)[]; FREEMAIL_CC(0.00)[vger.kernel.org,amd.com,gmail.com,joelfernandes.org,kernel.org,sony.com]; MIME_TRACE(0.00)[0:+]; FROM_EQ_ENVFROM(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; TO_MATCH_ENVRCPT_ALL(0.00)[]; FUZZY_BLOCKED(0.00)[rspamd.com]; DBL_BLOCKED_OPENRESOLVER(0.00)[monitor_work.work:url,imap1.dmz-prg2.suse.org:helo] X-Spam-Flag: NO X-Spam-Score: 0.41 On 8/1/24 13:10, Uladzislau Rezki (Sony) wrote: > Add a kvfree_rcu_barrier() function. It waits until all > in-flight pointers are freed over RCU machinery. It does > not wait any GP completion and it is within its right to > return immediately if there are no outstanding pointers. > > This function is useful when there is a need to guarantee > that a memory is fully freed before destroying memory caches. > For example, during unloading a kernel module. > > Signed-off-by: Uladzislau Rezki (Sony) Thanks a lot, Ulad! Locally it makde the kunit test stop failing and for now I've pushed it as part of my series for bots to test: https://git.kernel.org/pub/scm/linux/kernel/git/vbabka/linux.git/log/?h=slab-kfree_rcu-destroy-v2r0 I hope after RCU folks review I can carry this in my series and later the slab git tree so we don't have inter-tree dependencies. Thanks! Vlastimil > --- > include/linux/rcutiny.h | 5 ++ > include/linux/rcutree.h | 1 + > kernel/rcu/tree.c | 103 ++++++++++++++++++++++++++++++++++++---- > 3 files changed, 101 insertions(+), 8 deletions(-) > > diff --git a/include/linux/rcutiny.h b/include/linux/rcutiny.h > index d9ac7b136aea..522123050ff8 100644 > --- a/include/linux/rcutiny.h > +++ b/include/linux/rcutiny.h > @@ -111,6 +111,11 @@ static inline void __kvfree_call_rcu(struct rcu_head *head, void *ptr) > kvfree(ptr); > } > > +static inline void kvfree_rcu_barrier(void) > +{ > + rcu_barrier(); > +} > + > #ifdef CONFIG_KASAN_GENERIC > void kvfree_call_rcu(struct rcu_head *head, void *ptr); > #else > diff --git a/include/linux/rcutree.h b/include/linux/rcutree.h > index 254244202ea9..58e7db80f3a8 100644 > --- a/include/linux/rcutree.h > +++ b/include/linux/rcutree.h > @@ -35,6 +35,7 @@ static inline void rcu_virt_note_context_switch(void) > > void synchronize_rcu_expedited(void); > void kvfree_call_rcu(struct rcu_head *head, void *ptr); > +void kvfree_rcu_barrier(void); > > void rcu_barrier(void); > void rcu_momentary_dyntick_idle(void); > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c > index 28c7031711a3..1423013f9fe6 100644 > --- a/kernel/rcu/tree.c > +++ b/kernel/rcu/tree.c > @@ -3550,18 +3550,15 @@ kvfree_rcu_drain_ready(struct kfree_rcu_cpu *krcp) > } > > /* > - * This function is invoked after the KFREE_DRAIN_JIFFIES timeout. > + * Return: %true if a work is queued, %false otherwise. > */ > -static void kfree_rcu_monitor(struct work_struct *work) > +static bool > +kvfree_rcu_queue_batch(struct kfree_rcu_cpu *krcp) > { > - struct kfree_rcu_cpu *krcp = container_of(work, > - struct kfree_rcu_cpu, monitor_work.work); > unsigned long flags; > + bool queued = false; > int i, j; > > - // Drain ready for reclaim. > - kvfree_rcu_drain_ready(krcp); > - > raw_spin_lock_irqsave(&krcp->lock, flags); > > // Attempt to start a new batch. > @@ -3600,11 +3597,27 @@ static void kfree_rcu_monitor(struct work_struct *work) > // be that the work is in the pending state when > // channels have been detached following by each > // other. > - queue_rcu_work(system_wq, &krwp->rcu_work); > + queued = queue_rcu_work(system_wq, &krwp->rcu_work); > } > } > > raw_spin_unlock_irqrestore(&krcp->lock, flags); > + return queued; > +} > + > +/* > + * This function is invoked after the KFREE_DRAIN_JIFFIES timeout. > + */ > +static void kfree_rcu_monitor(struct work_struct *work) > +{ > + struct kfree_rcu_cpu *krcp = container_of(work, > + struct kfree_rcu_cpu, monitor_work.work); > + > + // Drain ready for reclaim. > + kvfree_rcu_drain_ready(krcp); > + > + // Queue a batch for a rest. > + kvfree_rcu_queue_batch(krcp); > > // If there is nothing to detach, it means that our job is > // successfully done here. In case of having at least one > @@ -3825,6 +3838,80 @@ void kvfree_call_rcu(struct rcu_head *head, void *ptr) > } > EXPORT_SYMBOL_GPL(kvfree_call_rcu); > > +/** > + * kvfree_rcu_barrier - Wait until all in-flight kvfree_rcu() complete. > + * > + * Note that a single argument of kvfree_rcu() call has a slow path that > + * triggers synchronize_rcu() following by freeing a pointer. It is done > + * before the return from the function. Therefore for any single-argument > + * call that will result in a kfree() to a cache that is to be destroyed > + * during module exit, it is developer's responsibility to ensure that all > + * such calls have returned before the call to kmem_cache_destroy(). > + */ > +void kvfree_rcu_barrier(void) > +{ > + struct kfree_rcu_cpu_work *krwp; > + struct kfree_rcu_cpu *krcp; > + bool queued; > + int i, cpu; > + > + /* > + * Firstly we detach objects and queue them over an RCU-batch > + * for all CPUs. Finally queued works are flushed for each CPU. > + * > + * Please note. If there are outstanding batches for a particular > + * CPU, those have to be finished first following by queuing a new. > + */ > + for_each_possible_cpu(cpu) { > + krcp = per_cpu_ptr(&krc, cpu); > + > + /* > + * Check if this CPU has any objects which have been queued for a > + * new GP completion. If not(means nothing to detach), we are done > + * with it. If any batch is pending/running for this "krcp", below > + * per-cpu flush_rcu_work() waits its completion(see last step). > + */ > + if (!need_offload_krc(krcp)) > + continue; > + > + while (1) { > + /* > + * If we are not able to queue a new RCU work it means: > + * - batches for this CPU are still in flight which should > + * be flushed first and then repeat; > + * - no objects to detach, because of concurrency. > + */ > + queued = kvfree_rcu_queue_batch(krcp); > + > + /* > + * Bail out, if there is no need to offload this "krcp" > + * anymore. As noted earlier it can run concurrently. > + */ > + if (queued || !need_offload_krc(krcp)) > + break; > + > + /* There are ongoing batches. */ > + for (i = 0; i < KFREE_N_BATCHES; i++) { > + krwp = &(krcp->krw_arr[i]); > + flush_rcu_work(&krwp->rcu_work); > + } > + } > + } > + > + /* > + * Now we guarantee that all objects are flushed. > + */ > + for_each_possible_cpu(cpu) { > + krcp = per_cpu_ptr(&krc, cpu); > + > + for (i = 0; i < KFREE_N_BATCHES; i++) { > + krwp = &(krcp->krw_arr[i]); > + flush_rcu_work(&krwp->rcu_work); > + } > + } > +} > +EXPORT_SYMBOL_GPL(kvfree_rcu_barrier); > + > static unsigned long > kfree_rcu_shrink_count(struct shrinker *shrink, struct shrink_control *sc) > {