kernel/linux.git/include/linux/rcupdate.h, branch v4.14.223

rcu: Force inlining of rcu_read_lock()

2019-07-31T05:28:25+00:00

[ Upstream commit 6da9f775175e516fc7229ceaa9b54f8f56aa7924 ] When debugging options are turned on, the rcu_read_lock() function might not be inlined. This results in lockdep's print_lock() function printing "rcu_read_lock+0x0/0x70" instead of rcu_read_lock()'s caller. For example: [ 10.579995] ============================= [ 10.584033] WARNING: suspicious RCU usage [ 10.588074] 4.18.0.memcg_v2+ #1 Not tainted [ 10.593162] ----------------------------- [ 10.597203] include/linux/rcupdate.h:281 Illegal context switch in RCU read-side critical section! [ 10.606220] [ 10.606220] other info that might help us debug this: [ 10.606220] [ 10.614280] [ 10.614280] rcu_scheduler_active = 2, debug_locks = 1 [ 10.620853] 3 locks held by systemd/1: [ 10.624632] #0: (____ptrval____) (&type->i_mutex_dir_key#5){.+.+}, at: lookup_slow+0x42/0x70 [ 10.633232] #1: (____ptrval____) (rcu_read_lock){....}, at: rcu_read_lock+0x0/0x70 [ 10.640954] #2: (____ptrval____) (rcu_read_lock){....}, at: rcu_read_lock+0x0/0x70 These "rcu_read_lock+0x0/0x70" strings are not providing any useful information. This commit therefore forces inlining of the rcu_read_lock() function so that rcu_read_lock()'s caller is instead shown. Signed-off-by: Waiman Long Signed-off-by: Paul E. McKenney Signed-off-by: Sasha Levin

rcu: locking and unlocking need to always be at least barriers

2019-06-11T10:21:47+00:00

commit 66be4e66a7f422128748e3c3ef6ee72b20a6197b upstream. Herbert Xu pointed out that commit bb73c52bad36 ("rcu: Don't disable preemption for Tiny and Tree RCU readers") was incorrect in making the preempt_disable/enable() be conditional on CONFIG_PREEMPT_COUNT. If CONFIG_PREEMPT_COUNT isn't enabled, the preemption enable/disable is a no-op, but still is a compiler barrier. And RCU locking still _needs_ that compiler barrier. It is simply fundamentally not true that RCU locking would be a complete no-op: we still need to guarantee (for example) that things that can trap and cause preemption cannot migrate into the RCU locked region. The way we do that is by making it a barrier. See for example commit 386afc91144b ("spinlocks and preemption points need to be at least compiler barriers") from back in 2013 that had similar issues with spinlocks that become no-ops on UP: they must still constrain the compiler from moving other operations into the critical region. Now, it is true that a lot of RCU operations already use READ_ONCE() and WRITE_ONCE() (which in practice likely would never be re-ordered wrt anything remotely interesting), but it is also true that that is not globally the case, and that it's not even necessarily always possible (ie bitfields etc). Reported-by: Herbert Xu Fixes: bb73c52bad36 ("rcu: Don't disable preemption for Tiny and Tree RCU readers") Cc: stable@kernel.org Cc: Boqun Feng Cc: Paul E. McKenney Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman

locking/barriers: Convert users of lockless_dereference() to READ_ONCE()

2017-12-25T13:26:21+00:00

commit 3382290ed2d5e275429cef510ab21889d3ccd164 upstream. [ Note, this is a Git cherry-pick of the following commit: 506458efaf15 ("locking/barriers: Convert users of lockless_dereference() to READ_ONCE()") ... for easier x86 PTI code testing and back-porting. ] READ_ONCE() now has an implicit smp_read_barrier_depends() call, so it can be used instead of lockless_dereference() without any change in semantics. Signed-off-by: Will Deacon Cc: Linus Torvalds Cc: Paul E. McKenney Cc: Peter Zijlstra Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/1508840570-22169-4-git-send-email-will.deacon@arm.com Signed-off-by: Ingo Molnar Signed-off-by: Greg Kroah-Hartman

doc: Fix various RCU docbook comment-header problems

2017-10-20T02:26:11+00:00

Because many of RCU's files have not been included into docbook, a number of errors have accumulated. This commit fixes them. Signed-off-by: Paul E. McKenney Signed-off-by: Linus Torvalds

Merge tag 'scsi-misc' of git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi

2017-09-08T04:11:05+00:00

Pull SCSI updates from James Bottomley: "This is mostly updates of the usual suspects: lpfc, qla2xxx, hisi_sas, megaraid_sas, zfcp and a host of minor updates. The major driver change here is the elimination of the block based cciss driver in favour of the SCSI based hpsa driver (which now drives all the legacy cases cciss used to be required for). Plus a reset handler clean up and the redo of the SAS SMP handler to use bsg lib" * tag 'scsi-misc' of git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi: (279 commits) scsi: scsi-mq: Always unprepare before requeuing a request scsi: Show .retries and .jiffies_at_alloc in debugfs scsi: Improve requeuing behavior scsi: Call scsi_initialize_rq() for filesystem requests scsi: qla2xxx: Reset the logo flag, after target re-login. scsi: qla2xxx: Fix slow mem alloc behind lock scsi: qla2xxx: Clear fc4f_nvme flag scsi: qla2xxx: add missing includes for qla_isr scsi: qla2xxx: Fix an integer overflow in sysfs code scsi: aacraid: report -ENOMEM to upper layer from aac_convert_sgraw2() scsi: aacraid: get rid of one level of indentation scsi: aacraid: fix indentation errors scsi: storvsc: fix memory leak on ring buffer busy scsi: scsi_transport_sas: switch to bsg-lib for SMP passthrough scsi: smartpqi: remove the smp_handler stub scsi: hpsa: remove the smp_handler stub scsi: bsg-lib: pass the release callback through bsg_setup_queue scsi: Rework handling of scsi_device.vpd_pg8[03] scsi: Rework the code for caching Vital Product Data (VPD) scsi: rcu: Introduce rcu_swap_protected() ...

scsi: rcu: Introduce rcu_swap_protected()

2017-08-30T01:51:41+00:00

A common pattern in RCU code is to assign a new value to an RCU pointer after having read and stored the old value. Introduce a macro for this pattern. Signed-off-by: Bart Van Assche Acked-by: Paul E. McKenney Cc: Christoph Hellwig Cc: Hannes Reinecke Cc: Johannes Thumshirn Cc: Shane M Seymour Signed-off-by: Martin K. Petersen

Merge branches 'doc.2017.08.17a', 'fixes.2017.08.17a', 'hotplug.2017.07.25b', 'misc.2017.08.17a', 'spin_unlock_wait_no.2017.08.17a', 'srcu.2017.07.27c' and 'torture.2017.07.24c' into HEAD

2017-08-17T15:10:04+00:00

doc.2017.08.17a: Documentation updates. fixes.2017.08.17a: RCU fixes. hotplug.2017.07.25b: CPU-hotplug updates. misc.2017.08.17a: Miscellaneous fixes outside of RCU (give or take conflicts). spin_unlock_wait_no.2017.08.17a: Remove spin_unlock_wait(). srcu.2017.07.27c: SRCU updates. torture.2017.07.24c: Torture-test updates.

rcu: Create reasonable API for do_exit() TASKS_RCU processing

2017-08-17T14:26:05+00:00

Currently, the exit-time support for TASKS_RCU is open-coded in do_exit(). This commit creates exit_tasks_rcu_start() and exit_tasks_rcu_finish() APIs for do_exit() use. This has the benefit of confining the use of the tasks_rcu_exit_srcu variable to one file, allowing it to become static. Signed-off-by: Paul E. McKenney

rcu: Drive TASKS_RCU directly off of PREEMPT

2017-08-17T14:26:04+00:00

The actual use of TASKS_RCU is only when PREEMPT, otherwise RCU-sched is used instead. This commit therefore makes synchronize_rcu_tasks() and call_rcu_tasks() available always, but mapped to synchronize_sched() and call_rcu_sched(), respectively, when !PREEMPT. This approach also allows some #ifdefs to be removed from rcutorture. Reported-by: Ingo Molnar Signed-off-by: Paul E. McKenney Reviewed-by: Masami Hiramatsu Acked-by: Ingo Molnar

rcu: Migrate callbacks earlier in the CPU-offline timeline

2017-07-25T20:03:43+00:00

RCU callbacks must be migrated away from an outgoing CPU, and this is done near the end of the CPU-hotplug operation, after the outgoing CPU is long gone. Unfortunately, this means that other CPU-hotplug callbacks can execute while the outgoing CPU's callbacks are still immobilized on the long-gone CPU's callback lists. If any of these CPU-hotplug callbacks must wait, either directly or indirectly, for the invocation of any of the immobilized RCU callbacks, the system will hang. This commit avoids such hangs by migrating the callbacks away from the outgoing CPU immediately upon its departure, shortly after the return from __cpu_die() in takedown_cpu(). Thus, RCU is able to advance these callbacks and invoke them, which allows all the after-the-fact CPU-hotplug callbacks to wait on these RCU callbacks without risk of a hang. While in the neighborhood, this commit also moves rcu_send_cbs_to_orphanage() and rcu_adopt_orphan_cbs() under a pre-existing #ifdef to avoid including dead code on the one hand and to avoid define-without-use warnings on the other hand. Reported-by: Jeffrey Hugo Link: http://lkml.kernel.org/r/db9c91f6-1b17-6136-84f0-03c3c2581ab4@codeaurora.org Signed-off-by: Paul E. McKenney Cc: Thomas Gleixner Cc: Sebastian Andrzej Siewior Cc: Ingo Molnar Cc: Anna-Maria Gleixner Cc: Boris Ostrovsky Cc: Richard Weinberger