Em Tue, Oct 10, 2017 at 02:59:18PM -0400, Dennis Dalessandro escreveu: > On 10/3/2017 11:49 AM, Arnaldo Carvalho de Melo wrote: > > From: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx> > > > > 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 <julia@xxxxxx> > > Cc: Clark Williams <williams@xxxxxxxxxx> > > Cc: Dean Luick <dean.luick@xxxxxxxxx> > > Cc: Dennis Dalessandro <dennis.dalessandro@xxxxxxxxx> > > Cc: Doug Ledford <dledford@xxxxxxxxxx> > > Cc: Kaike Wan <kaike.wan@xxxxxxxxx> > > Cc: Leon Romanovsky <leonro@xxxxxxxxxxxx> > > Cc: linux-rdma@xxxxxxxxxxxxxxx > > Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> > > Cc: Sebastian Andrzej Siewior <sebastian.siewior@xxxxxxxxxxxxx> > > Cc: Sebastian Sanchez <sebastian.sanchez@xxxxxxxxx> > > Cc: Steven Rostedt <rostedt@xxxxxxxxxxx> > > Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> > > Link: http://lkml.kernel.org/r/20170926210045.GO29872@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx > > Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx> > > 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 Right, and so far there were no strong objection for this one to be merged on the -rt tree, Sebastian, can you do it please? Adding Dennis' reviewed-by, one of maintainers for this driver, ok? > tree? Anyway, for this patch: > > Reviewed-by: Dennis Dalessandro <dennis.dalessandro@xxxxxxxxx> -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
