From 12e89c21dec793269a0c0f1f3f2160bb7cdf5ebd Mon Sep 17 00:00:00 2001 From: Sagar Kamble Date: Mon, 24 May 2021 14:36:01 +0530 Subject: gpu: nvgpu: fix the usermode mappings deadlock during railgate and munmap Following locking sequence leads to deadlock: 1. gk20a_pm_prepare_poweroff (alter_usermode_mappings): ctrl_privs_lock -> mmap_lock 2. __do_munmap (usermode_vma_close): mmap_lock -> ctrl_privs_lock This lock contention can be resolved by retrying the usermode mapping alteration after a while releasing the ctrl_priv_lock for munmap to proceed. Below is the kernel panic log with deadlock. [] INFO: task kworker/1:1:116 blocked for more than 120 seconds. [] Tainted: G W 5.10.17-tegra #1 [] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. [] task:kworker/1:1 state:D stack: 0 pid: 116 ppid: 2 flags:0x00000028 [] Workqueue: pm pm_runtime_work [] Call trace: [] __switch_to+0x104/0x160 [] __schedule+0x3d4/0x900 [] schedule+0x74/0x100 [] rwsem_down_write_slowpath+0x250/0x4b0 [] down_write+0x6c/0x80 [] alter_usermode_mappings+0xb4/0x160 [nvgpu] [] nvgpu_hide_usermode_for_poweroff+0x24/0x30 [nvgpu] [] gk20a_pm_prepare_poweroff+0xe8/0x140 [nvgpu] [] gk20a_pm_runtime_suspend+0x78/0xf0 [nvgpu] [] pm_generic_runtime_suspend+0x3c/0x60 [] genpd_runtime_suspend+0xb0/0x2c0 [] __rpm_callback+0x90/0x150 [] rpm_callback+0x34/0xa0 [] rpm_suspend+0xe0/0x5e0 [] pm_runtime_work+0xbc/0xc0 [] process_one_work+0x1c0/0x4a0 [] worker_thread+0x11c/0x430 [] kthread+0x148/0x170 [] ret_from_fork+0x10/0x18 [] INFO: task nvrm_gpu_tests:1273 blocked for more than 121 seconds. [] Tainted: G W 5.10.17-tegra #1 [] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. [] task:nvrm_gpu_tests state:D stack: 0 pid: 1273 ppid: 1245 flags:0x00000000 [] Call trace: [] __switch_to+0x104/0x160 [] __schedule+0x3d4/0x900 [] schedule+0x74/0x100 [] schedule_preempt_disabled+0x28/0x40 [] __mutex_lock.isra.0+0x184/0x5c0 [] __mutex_lock_slowpath+0x24/0x30 [] mutex_lock+0x5c/0x70 [] usermode_vma_close+0x30/0x50 [nvgpu] [] remove_vma+0x34/0x60 [] __do_munmap+0x1f4/0x4a0 [] __vm_munmap+0x74/0xd0 [] __arm64_sys_munmap+0x3c/0x50 [] el0_svc_common.constprop.0+0x7c/0x1a0 [] do_el0_svc+0x34/0xa0 [] el0_svc+0x1c/0x30 [] el0_sync_handler+0xa8/0xb0 [] el0_sync+0x160/0x180 [] ---[ end Kernel panic - not syncing: hung_task: blocked tasks ]--- Bug 200703921 Change-Id: Ie7f017c92f20061d3bf891079f7fc7fe390f7cf7 Signed-off-by: Sagar Kamble Reviewed-on: https://git-master.nvidia.com/r/c/linux-nvgpu/+/2533853 (cherry picked from commit 1dd3e0761c1995c88e9f8e1a26cf5eaf197510be) Reviewed-on: https://git-master.nvidia.com/r/c/linux-nvgpu/+/2540111 Reviewed-by: svc-mobile-coverity Reviewed-by: Bibek Basu Reviewed-by: mobile promotions GVS: Gerrit_Virtual_Submit Tested-by: mobile promotions --- drivers/gpu/nvgpu/os/linux/ioctl_ctrl.c | 52 ++++++++++++++++++++++++--------- 1 file changed, 39 insertions(+), 13 deletions(-) diff --git a/drivers/gpu/nvgpu/os/linux/ioctl_ctrl.c b/drivers/gpu/nvgpu/os/linux/ioctl_ctrl.c index f71921cb..b6cdffcb 100644 --- a/drivers/gpu/nvgpu/os/linux/ioctl_ctrl.c +++ b/drivers/gpu/nvgpu/os/linux/ioctl_ctrl.c @@ -2051,7 +2051,7 @@ int gk20a_ctrl_dev_mmap(struct file *filp, struct vm_area_struct *vma) return err; } -static void alter_usermode_mapping(struct gk20a *g, +static int alter_usermode_mapping(struct gk20a *g, struct gk20a_ctrl_priv *priv, bool poweroff) { @@ -2059,23 +2059,34 @@ static void alter_usermode_mapping(struct gk20a *g, struct vm_area_struct *vma = priv->usermode_vma.vma; bool vma_mapped = priv->usermode_vma.vma_mapped; u64 addr; - int err; + int err = 0; if (!vma) { /* Nothing to do - no mmap called */ - return; + return 0; } addr = l->regs_bus_addr + g->ops.fifo.usermode_base(g); - down_write(&vma->vm_mm->mmap_sem); - /* * This is a no-op for the below cases * a) poweroff and !vma_mapped - > do nothing as no map exists * b) !poweroff and vmap_mapped -> do nothing as already mapped */ - if (poweroff && vma_mapped) { + if (poweroff != vma_mapped) { + return 0; + } + + /* + * We use trylock due to lock inversion: we need to acquire + * mmap_lock while holding ctrl_privs_lock. usermode_vma_close + * does it in reverse order. Trylock is a way to avoid deadlock. + */ + if (!down_write_trylock(&vma->vm_mm->mmap_sem)) { + return -EBUSY; + } + + if (poweroff) { err = zap_vma_ptes(vma, vma->vm_start, SZ_4K); if (err == 0) { vma->vm_flags = VM_NONE; @@ -2083,7 +2094,7 @@ static void alter_usermode_mapping(struct gk20a *g, } else { nvgpu_err(g, "can't remove usermode mapping"); } - } else if (!poweroff && !vma_mapped) { + } else { vma->vm_flags = priv->usermode_vma.flags; err = io_remap_pfn_range(vma, vma->vm_start, addr >> PAGE_SHIFT, @@ -2097,19 +2108,34 @@ static void alter_usermode_mapping(struct gk20a *g, } up_write(&vma->vm_mm->mmap_sem); + + return err; } static void alter_usermode_mappings(struct gk20a *g, bool poweroff) { struct gk20a_ctrl_priv *priv; struct nvgpu_os_linux *l = nvgpu_os_linux_from_gk20a(g); + int err = 0; - nvgpu_mutex_acquire(&l->ctrl.privs_lock); - nvgpu_list_for_each_entry(priv, &l->ctrl.privs, - gk20a_ctrl_priv, list) { - alter_usermode_mapping(g, priv, poweroff); - } - nvgpu_mutex_release(&l->ctrl.privs_lock); + do { + nvgpu_mutex_acquire(&l->ctrl.privs_lock); + nvgpu_list_for_each_entry(priv, &l->ctrl.privs, + gk20a_ctrl_priv, list) { + err = alter_usermode_mapping(g, priv, poweroff); + if (err != 0) { + break; + } + } + nvgpu_mutex_release(&l->ctrl.privs_lock); + + if (err == -EBUSY) { + nvgpu_log_info(g, "ctrl_privs_lock lock contended. retry altering usermode mappings"); + nvgpu_udelay(10); + } else if (err != 0) { + nvgpu_err(g, "can't alter usermode mapping. err = %d", err); + } + } while (err == -EBUSY); } void nvgpu_hide_usermode_for_poweroff(struct gk20a *g) -- cgit v1.2.2