Messages in this thread | | | From | Ulf Hansson <> | Date | Tue, 29 Jun 2021 12:40:22 +0200 | Subject | Re: [PATCH v2] PM: domains: Shrink locking area of the gpd_list_lock |
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On Thu, 24 Jun 2021 at 22:18, Stephen Boyd <swboyd@chromium.org> wrote: > > On trogdor devices I see the following lockdep splat when stopping > youtube with lockdep enabled in the kernel. > > ====================================================== > WARNING: possible circular locking dependency detected > 5.13.0-rc2 #71 Not tainted > ------------------------------------------------------ > ThreadPoolSingl/3969 is trying to acquire lock: > ffffff80d4d5c080 (&inst->lock#3){+.+.}-{3:3}, at: vdec_buf_cleanup+0x3c/0x17c [venus_dec] > > but task is already holding lock: > ffffff80d3c3c4f8 (&q->mmap_lock){+.+.}-{3:3}, at: vb2_core_reqbufs+0xe4/0x390 [videobuf2_common] > > which lock already depends on the new lock. > > the existing dependency chain (in reverse order) is: > > -> #5 (&q->mmap_lock){+.+.}-{3:3}: > __mutex_lock_common+0xcc/0xb88 > mutex_lock_nested+0x5c/0x68 > vb2_mmap+0xf4/0x290 [videobuf2_common] > v4l2_m2m_fop_mmap+0x44/0x50 [v4l2_mem2mem] > v4l2_mmap+0x5c/0xa4 > mmap_region+0x310/0x5a4 > do_mmap+0x348/0x43c > vm_mmap_pgoff+0xfc/0x178 > ksys_mmap_pgoff+0x84/0xfc > __arm64_compat_sys_aarch32_mmap2+0x2c/0x38 > invoke_syscall+0x54/0x110 > el0_svc_common+0x88/0xf0 > do_el0_svc_compat+0x28/0x34 > el0_svc_compat+0x24/0x34 > el0_sync_compat_handler+0xc0/0xf0 > el0_sync_compat+0x19c/0x1c0 > > -> #4 (&mm->mmap_lock){++++}-{3:3}: > __might_fault+0x60/0x88 > filldir64+0x124/0x3a0 > dcache_readdir+0x7c/0x1ec > iterate_dir+0xc4/0x184 > __arm64_sys_getdents64+0x78/0x170 > invoke_syscall+0x54/0x110 > el0_svc_common+0xa8/0xf0 > do_el0_svc_compat+0x28/0x34 > el0_svc_compat+0x24/0x34 > el0_sync_compat_handler+0xc0/0xf0 > el0_sync_compat+0x19c/0x1c0 > > -> #3 (&sb->s_type->i_mutex_key#3){++++}-{3:3}: > down_write+0x94/0x1f4 > start_creating+0xb0/0x174 > debugfs_create_dir+0x28/0x138 > opp_debug_register+0x88/0xc0 > _add_opp_dev+0x84/0x9c > _add_opp_table_indexed+0x16c/0x310 > _of_add_table_indexed+0x70/0xb5c > dev_pm_opp_of_add_table_indexed+0x20/0x2c > of_genpd_add_provider_onecell+0xc4/0x1c8 > rpmhpd_probe+0x21c/0x278 > platform_probe+0xb4/0xd4 > really_probe+0x140/0x35c > driver_probe_device+0x90/0xcc > __device_attach_driver+0xa4/0xc0 > bus_for_each_drv+0x8c/0xd8 > __device_attach+0xc4/0x150 > device_initial_probe+0x20/0x2c > bus_probe_device+0x40/0xa4 > device_add+0x22c/0x3fc > of_device_add+0x44/0x54 > of_platform_device_create_pdata+0xb0/0xf4 > of_platform_bus_create+0x1d0/0x350 > of_platform_populate+0x80/0xd4 > devm_of_platform_populate+0x64/0xb0 > rpmh_rsc_probe+0x378/0x3dc > platform_probe+0xb4/0xd4 > really_probe+0x140/0x35c > driver_probe_device+0x90/0xcc > __device_attach_driver+0xa4/0xc0 > bus_for_each_drv+0x8c/0xd8 > __device_attach+0xc4/0x150 > device_initial_probe+0x20/0x2c > bus_probe_device+0x40/0xa4 > device_add+0x22c/0x3fc > of_device_add+0x44/0x54 > of_platform_device_create_pdata+0xb0/0xf4 > of_platform_bus_create+0x1d0/0x350 > of_platform_bus_create+0x21c/0x350 > of_platform_populate+0x80/0xd4 > of_platform_default_populate_init+0xb8/0xd4 > do_one_initcall+0x1b4/0x400 > do_initcall_level+0xa8/0xc8 > do_initcalls+0x5c/0x9c > do_basic_setup+0x2c/0x38 > kernel_init_freeable+0x1a4/0x1ec > kernel_init+0x20/0x118 > ret_from_fork+0x10/0x30 > > -> #2 (gpd_list_lock){+.+.}-{3:3}: > __mutex_lock_common+0xcc/0xb88 > mutex_lock_nested+0x5c/0x68 > __genpd_dev_pm_attach+0x70/0x18c > genpd_dev_pm_attach_by_id+0xe4/0x158 > genpd_dev_pm_attach_by_name+0x48/0x60 > dev_pm_domain_attach_by_name+0x2c/0x38 > dev_pm_opp_attach_genpd+0xac/0x160 > vcodec_domains_get+0x94/0x14c [venus_core] > core_get_v4+0x150/0x188 [venus_core] > venus_probe+0x138/0x444 [venus_core] > platform_probe+0xb4/0xd4 > really_probe+0x140/0x35c > driver_probe_device+0x90/0xcc > device_driver_attach+0x58/0x7c > __driver_attach+0xc8/0xe0 > bus_for_each_dev+0x88/0xd4 > driver_attach+0x30/0x3c > bus_add_driver+0x10c/0x1e0 > driver_register+0x70/0x108 > __platform_driver_register+0x30/0x3c > 0xffffffde113e1044 > do_one_initcall+0x1b4/0x400 > do_init_module+0x64/0x1fc > load_module+0x17f4/0x1958 > __arm64_sys_finit_module+0xb4/0xf0 > invoke_syscall+0x54/0x110 > el0_svc_common+0x88/0xf0 > do_el0_svc_compat+0x28/0x34 > el0_svc_compat+0x24/0x34 > el0_sync_compat_handler+0xc0/0xf0 > el0_sync_compat+0x19c/0x1c0 > > -> #1 (&opp_table->genpd_virt_dev_lock){+.+.}-{3:3}: > __mutex_lock_common+0xcc/0xb88 > mutex_lock_nested+0x5c/0x68 > _set_required_opps+0x74/0x120 > _set_opp+0x94/0x37c > dev_pm_opp_set_rate+0xa0/0x194 > core_clks_set_rate+0x28/0x58 [venus_core] > load_scale_v4+0x228/0x2b4 [venus_core] > session_process_buf+0x160/0x198 [venus_core] > venus_helper_vb2_buf_queue+0xcc/0x130 [venus_core] > vdec_vb2_buf_queue+0xc4/0x140 [venus_dec] > __enqueue_in_driver+0x164/0x188 [videobuf2_common] > vb2_core_qbuf+0x13c/0x47c [videobuf2_common] > vb2_qbuf+0x88/0xec [videobuf2_v4l2] > v4l2_m2m_qbuf+0x84/0x15c [v4l2_mem2mem] > v4l2_m2m_ioctl_qbuf+0x24/0x30 [v4l2_mem2mem] > v4l_qbuf+0x54/0x68 > __video_do_ioctl+0x2bc/0x3bc > video_usercopy+0x558/0xb04 > video_ioctl2+0x24/0x30 > v4l2_ioctl+0x58/0x68 > v4l2_compat_ioctl32+0x84/0xa0 > __arm64_compat_sys_ioctl+0x12c/0x140 > invoke_syscall+0x54/0x110 > el0_svc_common+0x88/0xf0 > do_el0_svc_compat+0x28/0x34 > el0_svc_compat+0x24/0x34 > el0_sync_compat_handler+0xc0/0xf0 > el0_sync_compat+0x19c/0x1c0 > > -> #0 (&inst->lock#3){+.+.}-{3:3}: > __lock_acquire+0x248c/0x2d6c > lock_acquire+0x240/0x314 > __mutex_lock_common+0xcc/0xb88 > mutex_lock_nested+0x5c/0x68 > vdec_buf_cleanup+0x3c/0x17c [venus_dec] > __vb2_queue_free+0x98/0x204 [videobuf2_common] > vb2_core_reqbufs+0x14c/0x390 [videobuf2_common] > vb2_reqbufs+0x58/0x74 [videobuf2_v4l2] > v4l2_m2m_reqbufs+0x58/0x90 [v4l2_mem2mem] > v4l2_m2m_ioctl_reqbufs+0x24/0x30 [v4l2_mem2mem] > v4l_reqbufs+0x58/0x6c > __video_do_ioctl+0x2bc/0x3bc > video_usercopy+0x558/0xb04 > video_ioctl2+0x24/0x30 > v4l2_ioctl+0x58/0x68 > v4l2_compat_ioctl32+0x84/0xa0 > __arm64_compat_sys_ioctl+0x12c/0x140 > invoke_syscall+0x54/0x110 > el0_svc_common+0x88/0xf0 > do_el0_svc_compat+0x28/0x34 > el0_svc_compat+0x24/0x34 > el0_sync_compat_handler+0xc0/0xf0 > el0_sync_compat+0x19c/0x1c0 > > other info that might help us debug this: > > Chain exists of: > &inst->lock#3 --> &mm->mmap_lock --> &q->mmap_lock > > Possible unsafe locking scenario: > > CPU0 CPU1 > ---- ---- > lock(&q->mmap_lock); > lock(&mm->mmap_lock); > lock(&q->mmap_lock); > lock(&inst->lock#3); > > *** DEADLOCK *** > > 1 lock held by ThreadPoolSingl/3969: > #0: ffffff80d3c3c4f8 (&q->mmap_lock){+.+.}-{3:3}, at: vb2_core_reqbufs+0xe4/0x390 [videobuf2_common] > > stack backtrace: > CPU: 2 PID: 3969 Comm: ThreadPoolSingl Not tainted 5.13.0-rc2 #71 > Hardware name: Google Lazor (rev3+) with KB Backlight (DT) > Call trace: > dump_backtrace+0x0/0x1b4 > show_stack+0x24/0x30 > dump_stack+0xe0/0x15c > print_circular_bug+0x32c/0x388 > check_noncircular+0x138/0x140 > __lock_acquire+0x248c/0x2d6c > lock_acquire+0x240/0x314 > __mutex_lock_common+0xcc/0xb88 > mutex_lock_nested+0x5c/0x68 > vdec_buf_cleanup+0x3c/0x17c [venus_dec] > __vb2_queue_free+0x98/0x204 [videobuf2_common] > vb2_core_reqbufs+0x14c/0x390 [videobuf2_common] > vb2_reqbufs+0x58/0x74 [videobuf2_v4l2] > v4l2_m2m_reqbufs+0x58/0x90 [v4l2_mem2mem] > v4l2_m2m_ioctl_reqbufs+0x24/0x30 [v4l2_mem2mem] > v4l_reqbufs+0x58/0x6c > __video_do_ioctl+0x2bc/0x3bc > video_usercopy+0x558/0xb04 > video_ioctl2+0x24/0x30 > v4l2_ioctl+0x58/0x68 > v4l2_compat_ioctl32+0x84/0xa0 > __arm64_compat_sys_ioctl+0x12c/0x140 > invoke_syscall+0x54/0x110 > el0_svc_common+0x88/0xf0 > do_el0_svc_compat+0x28/0x34 > el0_svc_compat+0x24/0x34 > el0_sync_compat_handler+0xc0/0xf0 > el0_sync_compat+0x19c/0x1c0 > > The 'gpd_list_lock' is nominally named as such to protect the 'gpd_list' > from concurrent access and mutation. Unfortunately, holding that mutex > around various OPP framework calls leads to lockdep splats because now > we're doing various operations in OPP core such as registering with > debugfs while holding the list lock. We don't need to hold any list > mutex while we're calling into OPP, so let's shrink the locking area of > the 'gpd_list_lock' so that lockdep isn't triggered. This also helps > reduce contention on this lock, which probably doesn't matter much but > at least is nice to have. > > Cc: Len Brown <len.brown@intel.com> > Cc: Pavel Machek <pavel@ucw.cz> > Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> > Cc: <linux-pm@vger.kernel.org> > Cc: Viresh Kumar <vireshk@kernel.org> > Signed-off-by: Stephen Boyd <swboyd@chromium.org>
Thanks for fixing this!
As I said, when discussing the previous version, I am working on additional improvements, but this should be a step in the right direction.
Reviewed-by: Ulf Hansson <ulf.hansson@linaro.org>
Kind regards Uffe
> --- > > Changes from v1: > * Removed list lock in genpd_add_provider() as it serves no purpose > > drivers/base/power/domain.c | 38 +++++++++++++++++-------------------- > 1 file changed, 17 insertions(+), 21 deletions(-) > > diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c > index b6a782c31613..03d18223d8bb 100644 > --- a/drivers/base/power/domain.c > +++ b/drivers/base/power/domain.c > @@ -1984,8 +1984,8 @@ int pm_genpd_init(struct generic_pm_domain *genpd, > > mutex_lock(&gpd_list_lock); > list_add(&genpd->gpd_list_node, &gpd_list); > - genpd_debug_add(genpd); > mutex_unlock(&gpd_list_lock); > + genpd_debug_add(genpd); > > return 0; > } > @@ -2172,12 +2172,19 @@ static int genpd_add_provider(struct device_node *np, genpd_xlate_t xlate, > > static bool genpd_present(const struct generic_pm_domain *genpd) > { > + bool ret = false; > const struct generic_pm_domain *gpd; > > - list_for_each_entry(gpd, &gpd_list, gpd_list_node) > - if (gpd == genpd) > - return true; > - return false; > + mutex_lock(&gpd_list_lock); > + list_for_each_entry(gpd, &gpd_list, gpd_list_node) { > + if (gpd == genpd) { > + ret = true; > + break; > + } > + } > + mutex_unlock(&gpd_list_lock); > + > + return ret; > } > > /** > @@ -2188,15 +2195,13 @@ static bool genpd_present(const struct generic_pm_domain *genpd) > int of_genpd_add_provider_simple(struct device_node *np, > struct generic_pm_domain *genpd) > { > - int ret = -EINVAL; > + int ret; > > if (!np || !genpd) > return -EINVAL; > > - mutex_lock(&gpd_list_lock); > - > if (!genpd_present(genpd)) > - goto unlock; > + return -EINVAL; > > genpd->dev.of_node = np; > > @@ -2207,7 +2212,7 @@ int of_genpd_add_provider_simple(struct device_node *np, > if (ret != -EPROBE_DEFER) > dev_err(&genpd->dev, "Failed to add OPP table: %d\n", > ret); > - goto unlock; > + return ret; > } > > /* > @@ -2225,16 +2230,13 @@ int of_genpd_add_provider_simple(struct device_node *np, > dev_pm_opp_of_remove_table(&genpd->dev); > } > > - goto unlock; > + return ret; > } > > genpd->provider = &np->fwnode; > genpd->has_provider = true; > > -unlock: > - mutex_unlock(&gpd_list_lock); > - > - return ret; > + return 0; > } > EXPORT_SYMBOL_GPL(of_genpd_add_provider_simple); > > @@ -2253,8 +2255,6 @@ int of_genpd_add_provider_onecell(struct device_node *np, > if (!np || !data) > return -EINVAL; > > - mutex_lock(&gpd_list_lock); > - > if (!data->xlate) > data->xlate = genpd_xlate_onecell; > > @@ -2294,8 +2294,6 @@ int of_genpd_add_provider_onecell(struct device_node *np, > if (ret < 0) > goto error; > > - mutex_unlock(&gpd_list_lock); > - > return 0; > > error: > @@ -2314,8 +2312,6 @@ int of_genpd_add_provider_onecell(struct device_node *np, > } > } > > - mutex_unlock(&gpd_list_lock); > - > return ret; > } > EXPORT_SYMBOL_GPL(of_genpd_add_provider_onecell); > > base-commit: d07f6ca923ea0927a1024dfccafc5b53b61cfecc > -- > https://chromeos.dev >
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