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gpu: nvgpu: fix the usermode mappings deadlock during railgate and munmap

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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 <skamble@nvidia.com>
Reviewed-on: https://git-master.nvidia.com/r/c/linux-nvgpu/+/2533853
Reviewed-by: svc_kernel_abi <svc_kernel_abi@nvidia.com>
Reviewed-by: Konsta Holtta <kholtta@nvidia.com>
Reviewed-by: Alex Waterman <alexw@nvidia.com>
Reviewed-by: mobile promotions <svcmobile_promotions@nvidia.com>
GVS: Gerrit_Virtual_Submit
Tested-by: mobile promotions <svcmobile_promotions@nvidia.com>
This commit is contained in:
Sagar Kamble
2021-05-24 14:36:01 +05:30
committed by mobile promotions
parent 419a65965b
commit 1dd3e0761c
1 changed files with 44 additions and 18 deletions
Download Patch File Download Diff File Expand all files Collapse all files

52
drivers/gpu/nvgpu/os/linux/ioctl_ctrl.c
View File

@@ -2300,31 +2300,42 @@ 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)
{
struct vm_area_struct *vma = priv->usermode_vma.vma;
bool vma_mapped = priv->usermode_vma.vma_mapped;
int err;
int err = 0;
if (!vma) {
/* Nothing to do - no mmap called */
return;
return 0;
}
#if LINUX_VERSION_CODE >= KERNEL_VERSION(5, 8, 0)
down_write(&vma->vm_mm->mmap_lock);
#else
down_write(&vma->vm_mm->mmap_sem);
#endif
/*
* 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 LINUX_VERSION_CODE >= KERNEL_VERSION(5, 8, 0)
if (!mmap_write_trylock(vma->vm_mm)) {
#else
if (!down_write_trylock(&vma->vm_mm->mmap_sem)) {
#endif
return -EBUSY;
}
if (poweroff) {
#if LINUX_VERSION_CODE >= KERNEL_VERSION(4, 18, 0)
zap_vma_ptes(vma, vma->vm_start, vma->vm_end - vma->vm_start);
err = 0;
@@ -2338,7 +2349,7 @@ 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,
g->usermode_regs_bus_addr >> PAGE_SHIFT,
@@ -2352,23 +2363,38 @@ static void alter_usermode_mapping(struct gk20a *g,
}
#if LINUX_VERSION_CODE >= KERNEL_VERSION(5, 8, 0)
up_write(&vma->vm_mm->mmap_lock);
mmap_write_unlock(vma->vm_mm);
#else
up_write(&vma->vm_mm->mmap_sem);
#endif
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;
do {
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);
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)