On 10/3/2017 11:49 AM, Arnaldo Carvalho de Melo wrote:
From: Arnaldo Carvalho de Melo <a...@redhat.com>sc_buffer_alloc() disables preemption that will be reenabled by either pio_copy() or seg_pio_copy_end(). But before disabling preemption it grabs a spin lock that will be dropped after it disables preemption, which ends up triggering a warning in migrate_disable() later on. spin_lock_irqsave(&sc->alloc_lock) migrate_disable() ++p->migrate_disable -> 2 preempt_disable() spin_unlock_irqrestore(&sc->alloc_lock) migrate_enable() in_atomic(), so just returns, migrate_disable stays at 2 spin_lock_irqsave(some other lock) -> b00m And the WARN_ON code ends up tripping over this over and over in log_store(). Sequence captured via ftrace_dump_on_oops + crash utility 'dmesg' command. [512258.613862] sm-3297 16 .....11 359465349134644: sc_buffer_alloc <-hfi1_verbs_send_pio [512258.613876] sm-3297 16 .....11 359465349134719: migrate_disable <-sc_buffer_alloc [512258.613890] sm-3297 16 .....12 359465349134798: rt_spin_lock <-sc_buffer_alloc [512258.613903] sm-3297 16 ....112 359465349135481: rt_spin_unlock <-sc_buffer_alloc [512258.613916] sm-3297 16 ....112 359465349135556: migrate_enable <-sc_buffer_alloc [512258.613935] sm-3297 16 ....112 359465349135788: seg_pio_copy_start <-hfi1_verbs_send_pio [512258.613954] sm-3297 16 ....112 359465349136273: update_sge <-hfi1_verbs_send_pio [512258.613981] sm-3297 16 ....112 359465349136373: seg_pio_copy_mid <-hfi1_verbs_send_pio [512258.613999] sm-3297 16 ....112 359465349136873: update_sge <-hfi1_verbs_send_pio [512258.614017] sm-3297 16 ....112 359465349136956: seg_pio_copy_mid <-hfi1_verbs_send_pio [512258.614035] sm-3297 16 ....112 359465349137221: seg_pio_copy_end <-hfi1_verbs_send_pio [512258.614048] sm-3297 16 .....12 359465349137360: migrate_disable <-hfi1_verbs_send_pio [512258.614065] sm-3297 16 .....12 359465349137476: warn_slowpath_null <-migrate_disable [512258.614081] sm-3297 16 .....12 359465349137564: __warn <-warn_slowpath_null [512258.614088] sm-3297 16 .....12 359465349137958: printk <-__warn [512258.614096] sm-3297 16 .....12 359465349138055: vprintk_default <-printk [512258.614104] sm-3297 16 .....12 359465349138144: vprintk_emit <-vprintk_default [512258.614111] sm-3297 16 d....12 359465349138312: _raw_spin_lock <-vprintk_emit [512258.614119] sm-3297 16 d...112 359465349138789: log_store <-vprintk_emit [512258.614127] sm-3297 16 .....12 359465349139068: migrate_disable <-vprintk_emit According to a discussion (see Link: below) on the linux-rt-users mailing list, this locking is done for performance reasons, not for correctness, so use the _nort() variants to avoid the above problem. Suggested-by: Julia Cartwright <ju...@ni.com> Cc: Clark Williams <willi...@redhat.com> Cc: Dean Luick <dean.lu...@intel.com> Cc: Dennis Dalessandro <dennis.dalessan...@intel.com> Cc: Doug Ledford <dledf...@redhat.com> Cc: Kaike Wan <kaike....@intel.com> Cc: Leon Romanovsky <leo...@mellanox.com> Cc: linux-r...@vger.kernel.org Cc: Peter Zijlstra <pet...@infradead.org> Cc: Sebastian Andrzej Siewior <sebastian.siew...@linutronix.de> Cc: Sebastian Sanchez <sebastian.sanc...@intel.com> Cc: Steven Rostedt <rost...@goodmis.org> Cc: Thomas Gleixner <t...@linutronix.de> Link: http://lkml.kernel.org/r/20170926210045.go29...@jcartwri.amer.corp.natinst.com Signed-off-by: Arnaldo Carvalho de Melo <a...@redhat.com>
I assume you are not asking for Doug to pick this up for linux-rdma and that this more of an RFC sort of deal and the intended destination is the -rt tree? Anyway, for this patch:
Reviewed-by: Dennis Dalessandro <dennis.dalessan...@intel.com>
