dri-devel March 2022

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[PATCH V1] drm/mediatek: Fix issue of vblank callback data is NULL
by Rex-BC Chen 21 Mar '22

21 Mar '22

We encountered a kernel panic issue that callback data will be NULL when it's using in ovl irq handler. There is a timing issue between mtk_disp_ovl_irq_handler() and mtk_ovl_disable_vblank(). To resolve this issue, we use the flow to register/unregister vblank cb: - Register callback function and callback data when crtc creates. - Unregister callback function and callback data when crtc destroies. With this solution, we can assure callback data will not be NULL when vblank is disable. Fixes: 9b0704988b15 ("drm/mediatek: Register vblank callback function") Signed-off-by: Rex-BC Chen <rex-bc.chen(a)mediatek.com> Reviewed-by: jason-jh.lin <jason-jh.lin(a)mediatek.com> --- drivers/gpu/drm/mediatek/mtk_disp_drv.h | 16 +++++++----- drivers/gpu/drm/mediatek/mtk_disp_ovl.c | 22 ++++++++++++---- drivers/gpu/drm/mediatek/mtk_disp_rdma.c | 20 +++++++++----- drivers/gpu/drm/mediatek/mtk_drm_crtc.c | 14 +++++++++- drivers/gpu/drm/mediatek/mtk_drm_ddp_comp.c | 4 +++ drivers/gpu/drm/mediatek/mtk_drm_ddp_comp.h | 29 ++++++++++++++++----- 6 files changed, 80 insertions(+), 25 deletions(-) diff --git a/drivers/gpu/drm/mediatek/mtk_disp_drv.h b/drivers/gpu/drm/mediatek/mtk_disp_drv.h index 86c3068894b1..974462831133 100644 --- a/drivers/gpu/drm/mediatek/mtk_disp_drv.h +++ b/drivers/gpu/drm/mediatek/mtk_disp_drv.h @@ -76,9 +76,11 @@ void mtk_ovl_layer_off(struct device *dev, unsigned int idx, void mtk_ovl_start(struct device *dev); void mtk_ovl_stop(struct device *dev); unsigned int mtk_ovl_supported_rotations(struct device *dev); -void mtk_ovl_enable_vblank(struct device *dev, - void (*vblank_cb)(void *), - void *vblank_cb_data); +void mtk_ovl_register_vblank_cb(struct device *dev, + void (*vblank_cb)(void *), + void *vblank_cb_data); +void mtk_ovl_unregister_vblank_cb(struct device *dev); +void mtk_ovl_enable_vblank(struct device *dev); void mtk_ovl_disable_vblank(struct device *dev); void mtk_rdma_bypass_shadow(struct device *dev); @@ -93,9 +95,11 @@ void mtk_rdma_layer_config(struct device *dev, unsigned int idx, struct cmdq_pkt *cmdq_pkt); void mtk_rdma_start(struct device *dev); void mtk_rdma_stop(struct device *dev); -void mtk_rdma_enable_vblank(struct device *dev, - void (*vblank_cb)(void *), - void *vblank_cb_data); +void mtk_rdma_register_vblank_cb(struct device *dev, + void (*vblank_cb)(void *), + void *vblank_cb_data); +void mtk_rdma_unregister_vblank_cb(struct device *dev); +void mtk_rdma_enable_vblank(struct device *dev); void mtk_rdma_disable_vblank(struct device *dev); #endif diff --git a/drivers/gpu/drm/mediatek/mtk_disp_ovl.c b/drivers/gpu/drm/mediatek/mtk_disp_ovl.c index 2146299e5f52..1fa1bbac9f9c 100644 --- a/drivers/gpu/drm/mediatek/mtk_disp_ovl.c +++ b/drivers/gpu/drm/mediatek/mtk_disp_ovl.c @@ -96,14 +96,28 @@ static irqreturn_t mtk_disp_ovl_irq_handler(int irq, void *dev_id) return IRQ_HANDLED; } -void mtk_ovl_enable_vblank(struct device *dev, - void (*vblank_cb)(void *), - void *vblank_cb_data) +void mtk_ovl_register_vblank_cb(struct device *dev, + void (*vblank_cb)(void *), + void *vblank_cb_data) { struct mtk_disp_ovl *ovl = dev_get_drvdata(dev); ovl->vblank_cb = vblank_cb; ovl->vblank_cb_data = vblank_cb_data; +} + +void mtk_ovl_unregister_vblank_cb(struct device *dev) +{ + struct mtk_disp_ovl *ovl = dev_get_drvdata(dev); + + ovl->vblank_cb = NULL; + ovl->vblank_cb_data = NULL; +} + +void mtk_ovl_enable_vblank(struct device *dev) +{ + struct mtk_disp_ovl *ovl = dev_get_drvdata(dev); + writel(0x0, ovl->regs + DISP_REG_OVL_INTSTA); writel_relaxed(OVL_FME_CPL_INT, ovl->regs + DISP_REG_OVL_INTEN); } @@ -112,8 +126,6 @@ void mtk_ovl_disable_vblank(struct device *dev) { struct mtk_disp_ovl *ovl = dev_get_drvdata(dev); - ovl->vblank_cb = NULL; - ovl->vblank_cb_data = NULL; writel_relaxed(0x0, ovl->regs + DISP_REG_OVL_INTEN); } diff --git a/drivers/gpu/drm/mediatek/mtk_disp_rdma.c b/drivers/gpu/drm/mediatek/mtk_disp_rdma.c index d41a3970b944..943780fc7bf6 100644 --- a/drivers/gpu/drm/mediatek/mtk_disp_rdma.c +++ b/drivers/gpu/drm/mediatek/mtk_disp_rdma.c @@ -94,24 +94,32 @@ static void rdma_update_bits(struct device *dev, unsigned int reg, writel(tmp, rdma->regs + reg); } -void mtk_rdma_enable_vblank(struct device *dev, - void (*vblank_cb)(void *), - void *vblank_cb_data) +void mtk_rdma_register_vblank_cb(struct device *dev, + void (*vblank_cb)(void *), + void *vblank_cb_data) { struct mtk_disp_rdma *rdma = dev_get_drvdata(dev); rdma->vblank_cb = vblank_cb; rdma->vblank_cb_data = vblank_cb_data; - rdma_update_bits(dev, DISP_REG_RDMA_INT_ENABLE, RDMA_FRAME_END_INT, - RDMA_FRAME_END_INT); } -void mtk_rdma_disable_vblank(struct device *dev) +void mtk_rdma_unregister_vblank_cb(struct device *dev) { struct mtk_disp_rdma *rdma = dev_get_drvdata(dev); rdma->vblank_cb = NULL; rdma->vblank_cb_data = NULL; +} + +void mtk_rdma_enable_vblank(struct device *dev) +{ + rdma_update_bits(dev, DISP_REG_RDMA_INT_ENABLE, RDMA_FRAME_END_INT, + RDMA_FRAME_END_INT); +} + +void mtk_rdma_disable_vblank(struct device *dev) +{ rdma_update_bits(dev, DISP_REG_RDMA_INT_ENABLE, RDMA_FRAME_END_INT, 0); } diff --git a/drivers/gpu/drm/mediatek/mtk_drm_crtc.c b/drivers/gpu/drm/mediatek/mtk_drm_crtc.c index d661edf7e0fe..e42a9bfa0ecb 100644 --- a/drivers/gpu/drm/mediatek/mtk_drm_crtc.c +++ b/drivers/gpu/drm/mediatek/mtk_drm_crtc.c @@ -152,6 +152,7 @@ static void mtk_drm_cmdq_pkt_destroy(struct cmdq_pkt *pkt) static void mtk_drm_crtc_destroy(struct drm_crtc *crtc) { struct mtk_drm_crtc *mtk_crtc = to_mtk_crtc(crtc); + int i; mtk_mutex_put(mtk_crtc->mutex); #if IS_REACHABLE(CONFIG_MTK_CMDQ) @@ -162,6 +163,14 @@ static void mtk_drm_crtc_destroy(struct drm_crtc *crtc) mtk_crtc->cmdq_client.chan = NULL; } #endif + + for (i = 0; i < mtk_crtc->ddp_comp_nr; i++) { + struct mtk_ddp_comp *comp; + + comp = mtk_crtc->ddp_comp[i]; + mtk_ddp_comp_unregister_vblank_cb(comp); + } + drm_crtc_cleanup(crtc); } @@ -616,7 +625,7 @@ static int mtk_drm_crtc_enable_vblank(struct drm_crtc *crtc) struct mtk_drm_crtc *mtk_crtc = to_mtk_crtc(crtc); struct mtk_ddp_comp *comp = mtk_crtc->ddp_comp[0]; - mtk_ddp_comp_enable_vblank(comp, mtk_crtc_ddp_irq, &mtk_crtc->base); + mtk_ddp_comp_enable_vblank(comp); return 0; } @@ -916,6 +925,9 @@ int mtk_drm_crtc_create(struct drm_device *drm_dev, if (comp->funcs->ctm_set) has_ctm = true; } + + mtk_ddp_comp_register_vblank_cb(comp, mtk_crtc_ddp_irq, + &mtk_crtc->base); } for (i = 0; i < mtk_crtc->ddp_comp_nr; i++) diff --git a/drivers/gpu/drm/mediatek/mtk_drm_ddp_comp.c b/drivers/gpu/drm/mediatek/mtk_drm_ddp_comp.c index b4b682bc1991..028cf76b9531 100644 --- a/drivers/gpu/drm/mediatek/mtk_drm_ddp_comp.c +++ b/drivers/gpu/drm/mediatek/mtk_drm_ddp_comp.c @@ -297,6 +297,8 @@ static const struct mtk_ddp_comp_funcs ddp_ovl = { .config = mtk_ovl_config, .start = mtk_ovl_start, .stop = mtk_ovl_stop, + .register_vblank_cb = mtk_ovl_register_vblank_cb, + .unregister_vblank_cb = mtk_ovl_unregister_vblank_cb, .enable_vblank = mtk_ovl_enable_vblank, .disable_vblank = mtk_ovl_disable_vblank, .supported_rotations = mtk_ovl_supported_rotations, @@ -321,6 +323,8 @@ static const struct mtk_ddp_comp_funcs ddp_rdma = { .config = mtk_rdma_config, .start = mtk_rdma_start, .stop = mtk_rdma_stop, + .register_vblank_cb = mtk_rdma_register_vblank_cb, + .unregister_vblank_cb = mtk_rdma_unregister_vblank_cb, .enable_vblank = mtk_rdma_enable_vblank, .disable_vblank = mtk_rdma_disable_vblank, .layer_nr = mtk_rdma_layer_nr, diff --git a/drivers/gpu/drm/mediatek/mtk_drm_ddp_comp.h b/drivers/gpu/drm/mediatek/mtk_drm_ddp_comp.h index 4c6a98662305..b83f24cb045f 100644 --- a/drivers/gpu/drm/mediatek/mtk_drm_ddp_comp.h +++ b/drivers/gpu/drm/mediatek/mtk_drm_ddp_comp.h @@ -48,9 +48,11 @@ struct mtk_ddp_comp_funcs { unsigned int bpc, struct cmdq_pkt *cmdq_pkt); void (*start)(struct device *dev); void (*stop)(struct device *dev); - void (*enable_vblank)(struct device *dev, - void (*vblank_cb)(void *), - void *vblank_cb_data); + void (*register_vblank_cb)(struct device *dev, + void (*vblank_cb)(void *), + void *vblank_cb_data); + void (*unregister_vblank_cb)(struct device *dev); + void (*enable_vblank)(struct device *dev); void (*disable_vblank)(struct device *dev); unsigned int (*supported_rotations)(struct device *dev); unsigned int (*layer_nr)(struct device *dev); @@ -111,12 +113,25 @@ static inline void mtk_ddp_comp_stop(struct mtk_ddp_comp *comp) comp->funcs->stop(comp->dev); } -static inline void mtk_ddp_comp_enable_vblank(struct mtk_ddp_comp *comp, - void (*vblank_cb)(void *), - void *vblank_cb_data) +static inline void mtk_ddp_comp_register_vblank_cb(struct mtk_ddp_comp *comp, + void (*vblank_cb)(void *), + void *vblank_cb_data) +{ + if (comp->funcs && comp->funcs->register_vblank_cb) + comp->funcs->register_vblank_cb(comp->dev, vblank_cb, + vblank_cb_data); +} + +static inline void mtk_ddp_comp_unregister_vblank_cb(struct mtk_ddp_comp *comp) +{ + if (comp->funcs && comp->funcs->unregister_vblank_cb) + comp->funcs->unregister_vblank_cb(comp->dev); +} + +static inline void mtk_ddp_comp_enable_vblank(struct mtk_ddp_comp *comp) { if (comp->funcs && comp->funcs->enable_vblank) - comp->funcs->enable_vblank(comp->dev, vblank_cb, vblank_cb_data); + comp->funcs->enable_vblank(comp->dev); } static inline void mtk_ddp_comp_disable_vblank(struct mtk_ddp_comp *comp) -- 2.18.0

2 2

[PATCH] drm/virtio: fix NULL pointer dereference in virtio_gpu_conn_get_modes
by Liu Zixian 21 Mar '22

21 Mar '22

drm_cvt_mode may return NULL and we should check it. This bug is found by syzkaller: FAULT_INJECTION stacktrace: [ 168.567394] FAULT_INJECTION: forcing a failure. name failslab, interval 1, probability 0, space 0, times 1 [ 168.567403] CPU: 1 PID: 6425 Comm: syz Kdump: loaded Not tainted 4.19.90-vhulk2201.1.0.h1035.kasan.eulerosv2r10.aarch64 #1 [ 168.567406] Hardware name: QEMU KVM Virtual Machine, BIOS 0.0.0 02/06/2015 [ 168.567408] Call trace: [ 168.567414] dump_backtrace+0x0/0x310 [ 168.567418] show_stack+0x28/0x38 [ 168.567423] dump_stack+0xec/0x15c [ 168.567427] should_fail+0x3ac/0x3d0 [ 168.567437] __should_failslab+0xb8/0x120 [ 168.567441] should_failslab+0x28/0xc0 [ 168.567445] kmem_cache_alloc_trace+0x50/0x640 [ 168.567454] drm_mode_create+0x40/0x90 [ 168.567458] drm_cvt_mode+0x48/0xc78 [ 168.567477] virtio_gpu_conn_get_modes+0xa8/0x140 [virtio_gpu] [ 168.567485] drm_helper_probe_single_connector_modes+0x3a4/0xd80 [ 168.567492] drm_mode_getconnector+0x2e0/0xa70 [ 168.567496] drm_ioctl_kernel+0x11c/0x1d8 [ 168.567514] drm_ioctl+0x558/0x6d0 [ 168.567522] do_vfs_ioctl+0x160/0xf30 [ 168.567525] ksys_ioctl+0x98/0xd8 [ 168.567530] __arm64_sys_ioctl+0x50/0xc8 [ 168.567536] el0_svc_common+0xc8/0x320 [ 168.567540] el0_svc_handler+0xf8/0x160 [ 168.567544] el0_svc+0x10/0x218 KASAN stacktrace: [ 168.567561] BUG: KASAN: null-ptr-deref in virtio_gpu_conn_get_modes+0xb4/0x140 [virtio_gpu] [ 168.567565] Read of size 4 at addr 0000000000000054 by task syz/6425 [ 168.567566] [ 168.567571] CPU: 1 PID: 6425 Comm: syz Kdump: loaded Not tainted 4.19.90-vhulk2201.1.0.h1035.kasan.eulerosv2r10.aarch64 #1 [ 168.567573] Hardware name: QEMU KVM Virtual Machine, BIOS 0.0.0 02/06/2015 [ 168.567575] Call trace: [ 168.567578] dump_backtrace+0x0/0x310 [ 168.567582] show_stack+0x28/0x38 [ 168.567586] dump_stack+0xec/0x15c [ 168.567591] kasan_report+0x244/0x2f0 [ 168.567594] __asan_load4+0x58/0xb0 [ 168.567607] virtio_gpu_conn_get_modes+0xb4/0x140 [virtio_gpu] [ 168.567612] drm_helper_probe_single_connector_modes+0x3a4/0xd80 [ 168.567617] drm_mode_getconnector+0x2e0/0xa70 [ 168.567621] drm_ioctl_kernel+0x11c/0x1d8 [ 168.567624] drm_ioctl+0x558/0x6d0 [ 168.567628] do_vfs_ioctl+0x160/0xf30 [ 168.567632] ksys_ioctl+0x98/0xd8 [ 168.567636] __arm64_sys_ioctl+0x50/0xc8 [ 168.567641] el0_svc_common+0xc8/0x320 [ 168.567645] el0_svc_handler+0xf8/0x160 [ 168.567649] el0_svc+0x10/0x218 Signed-off-by: Liu Zixian <liuzixian4(a)huawei.com> --- drivers/gpu/drm/virtio/virtgpu_display.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/drivers/gpu/drm/virtio/virtgpu_display.c b/drivers/gpu/drm/virtio/virtgpu_display.c index 5b00310ac..f73352e7b 100644 --- a/drivers/gpu/drm/virtio/virtgpu_display.c +++ b/drivers/gpu/drm/virtio/virtgpu_display.c @@ -179,6 +179,8 @@ static int virtio_gpu_conn_get_modes(struct drm_connector *connector) DRM_DEBUG("add mode: %dx%d\n", width, height); mode = drm_cvt_mode(connector->dev, width, height, 60, false, false, false); + if (!mode) + return count; mode->type |= DRM_MODE_TYPE_PREFERRED; drm_mode_probed_add(connector, mode); count++; -- 2.33.0

1 0

[PATCH v2] drm: Fix a infinite loop condition when order becomes 0
by Arunpravin Paneer Selvam 21 Mar '22

21 Mar '22

handle a situation in the condition order-- == min_order, when order = 0 and min_order = 0, leading to order = -1, it now won't exit the loop. To avoid this problem, added a order check in the same condition, (i.e) when order is 0, we return -ENOSPC v2: use full name in email program and in Signed-off tag Signed-off-by: Arunpravin Paneer Selvam <Arunpravin.PaneerSelvam(a)amd.com> --- drivers/gpu/drm/drm_buddy.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/gpu/drm/drm_buddy.c b/drivers/gpu/drm/drm_buddy.c index 72f52f293249..5ab66aaf2bbd 100644 --- a/drivers/gpu/drm/drm_buddy.c +++ b/drivers/gpu/drm/drm_buddy.c @@ -685,7 +685,7 @@ int drm_buddy_alloc_blocks(struct drm_buddy *mm, if (!IS_ERR(block)) break; - if (order-- == min_order) { + if (!order || order-- == min_order) { err = -ENOSPC; goto err_free; } base-commit: 3bd60c0259406c5ca3ce5cdc958fb910ad4b8175 -- 2.25.1

5 5

[PATCH] drm: add a check to verify the size alignment
by Arunpravin Paneer Selvam 21 Mar '22

21 Mar '22

add a simple check to reject any size not aligned to the min_page_size. Signed-off-by: Arunpravin Paneer Selvam <Arunpravin.PaneerSelvam(a)amd.com> --- drivers/gpu/drm/drm_buddy.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/drivers/gpu/drm/drm_buddy.c b/drivers/gpu/drm/drm_buddy.c index 72f52f293249..b503c88786b0 100644 --- a/drivers/gpu/drm/drm_buddy.c +++ b/drivers/gpu/drm/drm_buddy.c @@ -661,6 +661,9 @@ int drm_buddy_alloc_blocks(struct drm_buddy *mm, if (range_overflows(start, size, mm->size)) return -EINVAL; + if (WARN_ON(!IS_ALIGNED(size, min_page_size))) + return -EINVAL; + /* Actual range allocation */ if (start + size == end) return __drm_buddy_alloc_range(mm, start, size, blocks); -- 2.25.1

2 1

[PATCH] drm: Fix a infinite loop condition when order becomes 0
by Arunpravin 21 Mar '22

21 Mar '22

handle a situation in the condition order-- == min_order, when order = 0, leading to order = -1, it now won't exit the loop. To avoid this problem, added a order check in the same condition, (i.e) when order is 0, we return -ENOSPC Signed-off-by: Arunpravin <Arunpravin.PaneerSelvam(a)amd.com> --- drivers/gpu/drm/drm_buddy.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/gpu/drm/drm_buddy.c b/drivers/gpu/drm/drm_buddy.c index 72f52f293249..5ab66aaf2bbd 100644 --- a/drivers/gpu/drm/drm_buddy.c +++ b/drivers/gpu/drm/drm_buddy.c @@ -685,7 +685,7 @@ int drm_buddy_alloc_blocks(struct drm_buddy *mm, if (!IS_ERR(block)) break; - if (order-- == min_order) { + if (!order || order-- == min_order) { err = -ENOSPC; goto err_free; } -- 2.25.1

5 9

An announcement for kernel-global workqueue users.
by Tetsuo Handa 21 Mar '22

21 Mar '22

Hello. The Linux kernel provides kernel-global WQs (namely, system_wq, system_highpri_wq, system_long_wq, system_unbound_wq, system_freezable_wq, system_power_efficient_wq and system_freezable_power_efficient_wq). But since attempt to flush kernel-global WQs has possibility of deadlock, Tejun Heo thinks that we should stop calling flush_scheduled_work() and flush_workqueue(system_*). Such callers as of Linux 5.17 are listed below. ---------- $ git grep -nF 'flush_scheduled_work()' drivers/acpi/osl.c:1182: * invoke flush_scheduled_work()/acpi_os_wait_events_complete() to flush drivers/acpi/osl.c:1575: flush_scheduled_work(); drivers/block/aoe/aoedev.c:324: flush_scheduled_work(); drivers/block/aoe/aoedev.c:523: flush_scheduled_work(); drivers/crypto/atmel-ecc.c:401: flush_scheduled_work(); drivers/crypto/atmel-sha204a.c:162: flush_scheduled_work(); drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c:2606: flush_scheduled_work(); drivers/gpu/drm/bridge/lontium-lt9611uxc.c:985: flush_scheduled_work(); drivers/gpu/drm/i915/display/intel_display.c:10790: flush_scheduled_work(); drivers/gpu/drm/i915/gt/selftest_execlists.c:87: flush_scheduled_work(); drivers/iio/light/tsl2563.c:811: flush_scheduled_work(); drivers/infiniband/hw/mlx4/cm.c:511: flush_scheduled_work(); drivers/infiniband/hw/mlx4/cm.c:543: flush_scheduled_work(); /* make sure all timers were flushed */ drivers/infiniband/ulp/isert/ib_isert.c:2639: flush_scheduled_work(); drivers/input/mouse/psmouse-smbus.c:320: flush_scheduled_work(); drivers/md/dm.c:229: flush_scheduled_work(); drivers/message/fusion/mptscsih.c:1234: flush_scheduled_work(); drivers/net/phy/phy.c:1060: /* Cannot call flush_scheduled_work() here as desired because drivers/net/usb/lan78xx.c:3240: * can't flush_scheduled_work() until we drop rtnl (later), drivers/net/usb/usbnet.c:853: * can't flush_scheduled_work() until we drop rtnl (later), drivers/net/wireless/ath/ath6kl/usb.c:481: flush_scheduled_work(); drivers/net/wwan/wwan_hwsim.c:537: flush_scheduled_work(); /* Wait deletion works completion */ drivers/nvme/target/configfs.c:1557: flush_scheduled_work(); drivers/nvme/target/rdma.c:1587: flush_scheduled_work(); drivers/nvme/target/rdma.c:2056: flush_scheduled_work(); drivers/nvme/target/tcp.c:1818: flush_scheduled_work(); drivers/nvme/target/tcp.c:1879: flush_scheduled_work(); drivers/nvme/target/tcp.c:1884: flush_scheduled_work(); drivers/platform/surface/surface_acpi_notify.c:863: flush_scheduled_work(); drivers/power/supply/ab8500_btemp.c:975: flush_scheduled_work(); drivers/power/supply/ab8500_chargalg.c:1993: flush_scheduled_work(); drivers/power/supply/ab8500_charger.c:3400: flush_scheduled_work(); drivers/power/supply/ab8500_fg.c:3021: flush_scheduled_work(); drivers/rapidio/devices/tsi721.c:2944: flush_scheduled_work(); drivers/rtc/dev.c:99: flush_scheduled_work(); drivers/scsi/mpt3sas/mpt3sas_scsih.c:12409: flush_scheduled_work(); drivers/scsi/qla2xxx/qla_target.c:1568: flush_scheduled_work(); drivers/staging/olpc_dcon/olpc_dcon.c:386: flush_scheduled_work(); sound/soc/intel/atom/sst/sst.c:363: flush_scheduled_work(); $ git grep -nF 'flush_workqueue(system_' drivers/block/rnbd/rnbd-clt.c:1776: flush_workqueue(system_long_wq); drivers/infiniband/core/device.c:2857: flush_workqueue(system_unbound_wq); include/linux/workqueue.h:592: flush_workqueue(system_wq); ---------- I tried to send a patch that emits a warning when flushing kernel-global WQs is attempted ( https://lkml.kernel.org/r/2efd5461-fccd-f1d9-7138-0a6767cbf5fe@I-love.SAKUR… ). But Linus does not want such patch ( https://lkml.kernel.org/r/CAHk-=whWreGjEQ6yasspzBrNnS7EQiL+SknToWt=SzUh4Xom… ). Steps for converting kernel-global WQs into module's local WQs are shown below. But since an oversight in Step 4 results in breakage, I think that this conversion should be carefully handled by maintainers/developers of each module who are familiar with that module. (This is why I'm sending this mail than sending patches, in order to ask for your cooperation.) ---------- Step 0: Consider if flushing kernel-global WQs is unavoidable. For example, commit 081bdc9fe05bb232 ("RDMA/ib_srp: Fix a deadlock") simply removed flush_workqueue(system_long_wq) call. For another example, schedule_on_each_cpu() does not need to call flush_scheduled_work() because schedule_on_each_cpu() knows the list of all "struct work_struct" instances which need to be flushed using flush_work() call. If flushing kernel-global WQs is still unavoidable, please proceed to the following steps. Step 1: Declare a variable for your module. struct workqueue_struct *my_wq; Step 2: Create a WQ for your module from __init function. The same flags used by corresponding kernel-global WQ can be used when creating the WQ for your module. my_wq = alloc_workqueue("my_wq_name", 0, 0); Step 3: Destroy the WQ created in Step 2 from __exit function (and the error handling path of __init function if __init function may fail after creating the WQ). destroy_workqueue(my_wq); Step 4: Replace e.g. schedule_work() call with corresponding queue_work() call throughout your module which should be handled by the WQ for your module. Step 5: Replace flush_scheduled_work() and flush_workqueue(system_*) calls with flush_workqueue() of the WQ for your module. flush_workqueue(my_wq); ---------- Regards.

1 0

[PATCH v4 00/24] DEPT(Dependency Tracker)
by Byungchul Park 20 Mar '22

20 Mar '22

Hi Linus and folks, I've been developing a tool for detecting deadlock possibilities by tracking wait/event rather than lock(?) acquisition order to try to cover all synchonization machanisms. It's done on v5.17-rc1 tag. https://github.com/lgebyungchulpark/linux-dept/commits/dept1.14_on_v5.17-rc1 Benifit: 0. Works with all lock primitives. 1. Works with wait_for_completion()/complete(). 2. Works with 'wait' on PG_locked. 3. Works with 'wait' on PG_writeback. 4. Works with swait/wakeup. 5. Works with waitqueue. 6. Multiple reports are allowed. 7. Deduplication control on multiple reports. 8. Withstand false positives thanks to 6. 9. Easy to tag any wait/event. Future work: 0. To make it more stable. 1. To separates Dept from Lockdep. 2. To improves performance in terms of time and space. 3. To use Dept as a dependency engine for Lockdep. 4. To add any missing tags of wait/event in the kernel. 5. To deduplicate stack trace. How to interpret reports: 1. E(event) in each context cannot be triggered because of the W(wait) that cannot be woken. 2. The stack trace helping find the problematic code is located in each conext's detail. Thanks, Byungchul --- Changes from v3: 1. Dept shouldn't create dependencies between different depths of a class that were indicated by *_lock_nested(). Dept normally doesn't but it does once another lock class comes in. So fixed it. (feedback from Hyeonggon) 2. Dept considered a wait as a real wait once getting to __schedule() even if it has been set to TASK_RUNNING by wake up sources in advance. Fixed it so that Dept doesn't consider the case as a real wait. (feedback from Jan Kara) 3. Stop tracking dependencies with a map once the event associated with the map has been handled. Dept will start to work with the map again, on the next sleep. Changes from v2: 1. Disable Dept on bit_wait_table[] in sched/wait_bit.c reporting a lot of false positives, which is my fault. Wait/event for bit_wait_table[] should've been tagged in a higher layer for better work, which is a future work. (feedback from Jan Kara) 2. Disable Dept on crypto_larval's completion to prevent a false positive. Changes from v1: 1. Fix coding style and typo. (feedback from Steven) 2. Distinguish each work context from another in workqueue. 3. Skip checking lock acquisition with nest_lock, which is about correct lock usage that should be checked by Lockdep. Changes from RFC: 1. Prevent adding a wait tag at prepare_to_wait() but __schedule(). (feedback from Linus and Matthew) 2. Use try version at lockdep_acquire_cpus_lock() annotation. 3. Distinguish each syscall context from another. Byungchul Park (24): llist: Move llist_{head,node} definition to types.h dept: Implement Dept(Dependency Tracker) dept: Embed Dept data in Lockdep dept: Add a API for skipping dependency check temporarily dept: Apply Dept to spinlock dept: Apply Dept to mutex families dept: Apply Dept to rwlock dept: Apply Dept to wait_for_completion()/complete() dept: Apply Dept to seqlock dept: Apply Dept to rwsem dept: Add proc knobs to show stats and dependency graph dept: Introduce split map concept and new APIs for them dept: Apply Dept to wait/event of PG_{locked,writeback} dept: Apply SDT to swait dept: Apply SDT to wait(waitqueue) locking/lockdep, cpu/hotplus: Use a weaker annotation in AP thread dept: Distinguish each syscall context from another dept: Distinguish each work from another dept: Disable Dept within the wait_bit layer by default dept: Add nocheck version of init_completion() dept: Disable Dept on struct crypto_larval's completion for now dept: Don't create dependencies between different depths in any case dept: Let it work with real sleeps in __schedule() dept: Disable Dept on that map once it's been handled until next turn crypto/api.c | 7 +- include/linux/completion.h | 50 +- include/linux/dept.h | 535 +++++++ include/linux/dept_page.h | 78 ++ include/linux/dept_sdt.h | 62 + include/linux/hardirq.h | 3 + include/linux/irqflags.h | 33 +- include/linux/llist.h | 8 - include/linux/lockdep.h | 158 ++- include/linux/lockdep_types.h | 3 + include/linux/mutex.h | 33 + include/linux/page-flags.h | 45 +- include/linux/pagemap.h | 7 +- include/linux/percpu-rwsem.h | 10 +- include/linux/rtmutex.h | 7 + include/linux/rwlock.h | 52 + include/linux/rwlock_api_smp.h | 8 +- include/linux/rwlock_types.h | 7 + include/linux/rwsem.h | 33 + include/linux/sched.h | 7 + include/linux/seqlock.h | 59 +- include/linux/spinlock.h | 26 + include/linux/spinlock_types_raw.h | 13 + include/linux/swait.h | 4 + include/linux/types.h | 8 + include/linux/wait.h | 6 +- init/init_task.c | 2 + init/main.c | 4 + kernel/Makefile | 1 + kernel/cpu.c | 2 +- kernel/dependency/Makefile | 4 + kernel/dependency/dept.c | 2716 ++++++++++++++++++++++++++++++++++++ kernel/dependency/dept_hash.h | 10 + kernel/dependency/dept_internal.h | 26 + kernel/dependency/dept_object.h | 13 + kernel/dependency/dept_proc.c | 92 ++ kernel/entry/common.c | 3 + kernel/exit.c | 1 + kernel/fork.c | 2 + kernel/locking/lockdep.c | 12 +- kernel/module.c | 2 + kernel/sched/completion.c | 12 +- kernel/sched/core.c | 8 + kernel/sched/swait.c | 10 + kernel/sched/wait.c | 16 + kernel/sched/wait_bit.c | 5 +- kernel/softirq.c | 6 +- kernel/trace/trace_preemptirq.c | 19 +- kernel/workqueue.c | 3 + lib/Kconfig.debug | 21 + mm/filemap.c | 68 + mm/page_ext.c | 5 + 52 files changed, 4266 insertions(+), 59 deletions(-) create mode 100644 include/linux/dept.h create mode 100644 include/linux/dept_page.h create mode 100644 include/linux/dept_sdt.h create mode 100644 kernel/dependency/Makefile create mode 100644 kernel/dependency/dept.c create mode 100644 kernel/dependency/dept_hash.h create mode 100644 kernel/dependency/dept_internal.h create mode 100644 kernel/dependency/dept_object.h create mode 100644 kernel/dependency/dept_proc.c -- 1.9.1

3 35

[PATCH RFC v5 00/21] DEPT(Dependency Tracker)
by Byungchul Park 20 Mar '22

20 Mar '22

I'm gonna re-add RFC for a while at Ted's request. But hard testing is needed to find false alarms for now that there's no false alarm with my system. I'm gonna look for other systems that might produce false alarms. And it'd be appreciated if you share it when you see any alarms with yours. --- Hi Linus and folks, I've been developing a tool for detecting deadlock possibilities by tracking wait/event rather than lock(?) acquisition order to try to cover all synchonization machanisms. It's done on v5.17-rc7 tag. https://github.com/lgebyungchulpark/linux-dept/commits/dept1.18_on_v5.17-rc7 Benifit: 0. Works with all lock primitives. 1. Works with wait_for_completion()/complete(). 2. Works with 'wait' on PG_locked. 3. Works with 'wait' on PG_writeback. 4. Works with swait/wakeup. 5. Works with waitqueue. 6. Multiple reports are allowed. 7. Deduplication control on multiple reports. 8. Withstand false positives thanks to 6. 9. Easy to tag any wait/event. Future work: 0. To make it more stable. 1. To separates Dept from Lockdep. 2. To improves performance in terms of time and space. 3. To use Dept as a dependency engine for Lockdep. 4. To add any missing tags of wait/event in the kernel. 5. To deduplicate stack trace. How to interpret reports: 1. E(event) in each context cannot be triggered because of the W(wait) that cannot be woken. 2. The stack trace helping find the problematic code is located in each conext's detail. Thanks, Byungchul --- Changes from v4: 1. Fix some bugs that produce false alarms. 2. Distinguish each syscall context from another *for arm64*. 3. Make it not warn it but just print it in case Dept ring buffer gets exhausted. (feedback from Hyeonggon) 4. Explicitely describe "EXPERIMENTAL" and "Dept might produce false positive reports" in Kconfig. (feedback from Ted) Changes from v3: 1. Dept shouldn't create dependencies between different depths of a class that were indicated by *_lock_nested(). Dept normally doesn't but it does once another lock class comes in. So fixed it. (feedback from Hyeonggon) 2. Dept considered a wait as a real wait once getting to __schedule() even if it has been set to TASK_RUNNING by wake up sources in advance. Fixed it so that Dept doesn't consider the case as a real wait. (feedback from Jan Kara) 3. Stop tracking dependencies with a map once the event associated with the map has been handled. Dept will start to work with the map again, on the next sleep. Changes from v2: 1. Disable Dept on bit_wait_table[] in sched/wait_bit.c reporting a lot of false positives, which is my fault. Wait/event for bit_wait_table[] should've been tagged in a higher layer for better work, which is a future work. (feedback from Jan Kara) 2. Disable Dept on crypto_larval's completion to prevent a false positive. Changes from v1: 1. Fix coding style and typo. (feedback from Steven) 2. Distinguish each work context from another in workqueue. 3. Skip checking lock acquisition with nest_lock, which is about correct lock usage that should be checked by Lockdep. Changes from RFC: 1. Prevent adding a wait tag at prepare_to_wait() but __schedule(). (feedback from Linus and Matthew) 2. Use try version at lockdep_acquire_cpus_lock() annotation. 3. Distinguish each syscall context from another. Byungchul Park (21): llist: Move llist_{head,node} definition to types.h dept: Implement Dept(Dependency Tracker) dept: Embed Dept data in Lockdep dept: Apply Dept to spinlock dept: Apply Dept to mutex families dept: Apply Dept to rwlock dept: Apply Dept to wait_for_completion()/complete() dept: Apply Dept to seqlock dept: Apply Dept to rwsem dept: Add proc knobs to show stats and dependency graph dept: Introduce split map concept and new APIs for them dept: Apply Dept to wait/event of PG_{locked,writeback} dept: Apply SDT to swait dept: Apply SDT to wait(waitqueue) locking/lockdep, cpu/hotplus: Use a weaker annotation in AP thread dept: Distinguish each syscall context from another dept: Distinguish each work from another dept: Disable Dept within the wait_bit layer by default dept: Add nocheck version of init_completion() dept: Disable Dept on struct crypto_larval's completion for now dept: Don't create dependencies between different depths in any case arch/arm64/kernel/syscall.c | 2 + arch/x86/entry/common.c | 4 + crypto/api.c | 7 +- include/linux/completion.h | 50 +- include/linux/dept.h | 544 +++++++ include/linux/dept_page.h | 78 + include/linux/dept_sdt.h | 62 + include/linux/hardirq.h | 3 + include/linux/irqflags.h | 33 +- include/linux/llist.h | 8 - include/linux/lockdep.h | 157 ++- include/linux/lockdep_types.h | 3 + include/linux/mutex.h | 32 + include/linux/page-flags.h | 45 +- include/linux/pagemap.h | 7 +- include/linux/percpu-rwsem.h | 10 +- include/linux/rtmutex.h | 7 + include/linux/rwlock.h | 50 + include/linux/rwlock_api_smp.h | 8 +- include/linux/rwlock_types.h | 7 + include/linux/rwsem.h | 32 + include/linux/sched.h | 7 + include/linux/seqlock.h | 68 +- include/linux/spinlock.h | 25 + include/linux/spinlock_types_raw.h | 13 + include/linux/swait.h | 4 + include/linux/types.h | 8 + include/linux/wait.h | 6 +- init/init_task.c | 2 + init/main.c | 4 + kernel/Makefile | 1 + kernel/cpu.c | 2 +- kernel/dependency/Makefile | 4 + kernel/dependency/dept.c | 2743 ++++++++++++++++++++++++++++++++++++ kernel/dependency/dept_hash.h | 10 + kernel/dependency/dept_internal.h | 26 + kernel/dependency/dept_object.h | 13 + kernel/dependency/dept_proc.c | 92 ++ kernel/exit.c | 1 + kernel/fork.c | 2 + kernel/locking/lockdep.c | 12 +- kernel/module.c | 2 + kernel/sched/completion.c | 12 +- kernel/sched/core.c | 8 + kernel/sched/swait.c | 10 + kernel/sched/wait.c | 16 + kernel/sched/wait_bit.c | 5 +- kernel/softirq.c | 6 +- kernel/trace/trace_preemptirq.c | 19 +- kernel/workqueue.c | 3 + lib/Kconfig.debug | 27 + mm/filemap.c | 68 + mm/page_ext.c | 5 + 53 files changed, 4313 insertions(+), 60 deletions(-) create mode 100644 include/linux/dept.h create mode 100644 include/linux/dept_page.h create mode 100644 include/linux/dept_sdt.h create mode 100644 kernel/dependency/Makefile create mode 100644 kernel/dependency/dept.c create mode 100644 kernel/dependency/dept_hash.h create mode 100644 kernel/dependency/dept_internal.h create mode 100644 kernel/dependency/dept_object.h create mode 100644 kernel/dependency/dept_proc.c -- 1.9.1

2 25

[RFC PATCH] drm: bridge: adv7511: get edid in hpd_work to update CEC phys address
by Alvin Šipraga 19 Mar '22

19 Mar '22

From: Alvin Šipraga <alsi(a)bang-olufsen.dk> The adv7511 driver is solely responsible for setting the physical address of its CEC adapter. To do this, it must read the EDID. However, EDID is only read when either the drm_bridge_funcs :: get_edid or drm_connector_helper_funcs :: get_modes ops are called. Without loss of generality, it cannot be assumed that these ops are called when a sink gets attached. Therefore there exist scenarios in which the CEC physical address will be invalid (f.f.f.f), rendering the CEC adapter inoperable. Address this problem by always fetching the EDID in the HPD work when we detect a connection. The CEC physical address is set in the process. Signed-off-by: Alvin Šipraga <alsi(a)bang-olufsen.dk> --- Hi, I'm sending this as an RFC patch because: - The added prototype is a bit crude, but I want feedback on the idea first before moving around a bunch of functions to avoid said prototype - I'm not sure if the rationale stated above is correct. I am not very familiar with the drm subsystem so perhaps there is something obvious that I am missing. At any rate, this solved the issue of an inoperable CEC adapter when the downstream MIPI-DSI was not used. I'm also wondering if this is robust enough to work when a sink just pulses HPD to signal that its EDID has changed. Currently the hotplug notifier is only invoked when the connected state changes (e.g. from disconnected to connected), and so I only check the EDID in such scenarios too. But is that always the case? Might we get an HPD interrupt and the connectivity state remains the same? Thanks in advance for any feedback. --- drivers/gpu/drm/bridge/adv7511/adv7511_drv.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c b/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c index 005bf18682ff..fb4ca277e4be 100644 --- a/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c +++ b/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c @@ -424,6 +424,9 @@ static bool adv7511_hpd(struct adv7511 *adv7511) return false; } +static struct edid *adv7511_get_edid(struct adv7511 *adv7511, + struct drm_connector *connector); + static void adv7511_hpd_work(struct work_struct *work) { struct adv7511 *adv7511 = container_of(work, struct adv7511, hpd_work); @@ -457,6 +460,9 @@ static void adv7511_hpd_work(struct work_struct *work) if (adv7511->connector.dev) { if (status == connector_status_disconnected) cec_phys_addr_invalidate(adv7511->cec_adap); + else + adv7511_get_edid(adv7511, &adv7511->connector); + drm_kms_helper_hotplug_event(adv7511->connector.dev); } else { drm_bridge_hpd_notify(&adv7511->bridge, status); -- 2.35.1

1 0

[PATCH 0/2] drm: bridge: adv7511: two fixes for CEC
by Alvin Šipraga 19 Mar '22

19 Mar '22

From: Alvin Šipraga <alsi(a)bang-olufsen.dk> The patches are sent against drm-misc-next. Thanks! Alvin Šipraga (2): drm: bridge: adv7511: fix CEC power down control register offset drm: bridge: adv7511: unregister cec i2c device after cec adapter drivers/gpu/drm/bridge/adv7511/adv7511.h | 5 +---- drivers/gpu/drm/bridge/adv7511/adv7511_cec.c | 4 ++-- drivers/gpu/drm/bridge/adv7511/adv7511_drv.c | 5 ++--- 3 files changed, 5 insertions(+), 9 deletions(-) -- 2.35.1

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dri-devel March 2022