[drm-intel:drm-intel-gt-next 8/14] drivers/gpu/drm/i915/gt/selftest_migrate.c:102 copy() error: uninitialized symbol 'rq'.
tree: git://anongit.freedesktop.org/drm-intel drm-intel-gt-next head: 5cd57f676bb946a00275408f0dd0d75dbc466d25 commit: cf586021642d8017cde111b7dd1ba86224e9da51 [8/14] drm/i915/gt: Pipelined page migration config: x86_64-randconfig-m001-20210630 (attached as .config) compiler: gcc-9 (Debian 9.3.0-22) 9.3.0
If you fix the issue, kindly add following tag as appropriate Reported-by: kernel test robot lkp@intel.com Reported-by: Dan Carpenter dan.carpenter@oracle.com
New smatch warnings: drivers/gpu/drm/i915/gt/selftest_migrate.c:102 copy() error: uninitialized symbol 'rq'. drivers/gpu/drm/i915/gt/selftest_migrate.c:113 copy() error: uninitialized symbol 'vaddr'.
Old smatch warnings: drivers/gpu/drm/i915/gem/i915_gem_object.h:182 __i915_gem_object_lock() error: we previously assumed 'ww' could be null (see line 171)
vim +/rq +102 drivers/gpu/drm/i915/gt/selftest_migrate.c
cf586021642d80 Chris Wilson 2021-06-17 32 static int copy(struct intel_migrate *migrate, cf586021642d80 Chris Wilson 2021-06-17 33 int (*fn)(struct intel_migrate *migrate, cf586021642d80 Chris Wilson 2021-06-17 34 struct i915_gem_ww_ctx *ww, cf586021642d80 Chris Wilson 2021-06-17 35 struct drm_i915_gem_object *src, cf586021642d80 Chris Wilson 2021-06-17 36 struct drm_i915_gem_object *dst, cf586021642d80 Chris Wilson 2021-06-17 37 struct i915_request **out), cf586021642d80 Chris Wilson 2021-06-17 38 u32 sz, struct rnd_state *prng) cf586021642d80 Chris Wilson 2021-06-17 39 { cf586021642d80 Chris Wilson 2021-06-17 40 struct drm_i915_private *i915 = migrate->context->engine->i915; cf586021642d80 Chris Wilson 2021-06-17 41 struct drm_i915_gem_object *src, *dst; cf586021642d80 Chris Wilson 2021-06-17 42 struct i915_request *rq; cf586021642d80 Chris Wilson 2021-06-17 43 struct i915_gem_ww_ctx ww; cf586021642d80 Chris Wilson 2021-06-17 44 u32 *vaddr; cf586021642d80 Chris Wilson 2021-06-17 45 int err = 0;
One way to silence these warnings would be to initialize err = -EINVAL. Then Smatch would know that we goto err_out for an empty list.
cf586021642d80 Chris Wilson 2021-06-17 46 int i; cf586021642d80 Chris Wilson 2021-06-17 47 cf586021642d80 Chris Wilson 2021-06-17 48 src = create_lmem_or_internal(i915, sz); cf586021642d80 Chris Wilson 2021-06-17 49 if (IS_ERR(src)) cf586021642d80 Chris Wilson 2021-06-17 50 return 0; cf586021642d80 Chris Wilson 2021-06-17 51 cf586021642d80 Chris Wilson 2021-06-17 52 dst = i915_gem_object_create_internal(i915, sz); cf586021642d80 Chris Wilson 2021-06-17 53 if (IS_ERR(dst)) cf586021642d80 Chris Wilson 2021-06-17 54 goto err_free_src; cf586021642d80 Chris Wilson 2021-06-17 55 cf586021642d80 Chris Wilson 2021-06-17 56 for_i915_gem_ww(&ww, err, true) { cf586021642d80 Chris Wilson 2021-06-17 57 err = i915_gem_object_lock(src, &ww); cf586021642d80 Chris Wilson 2021-06-17 58 if (err) cf586021642d80 Chris Wilson 2021-06-17 59 continue; cf586021642d80 Chris Wilson 2021-06-17 60 cf586021642d80 Chris Wilson 2021-06-17 61 err = i915_gem_object_lock(dst, &ww); cf586021642d80 Chris Wilson 2021-06-17 62 if (err) cf586021642d80 Chris Wilson 2021-06-17 63 continue; cf586021642d80 Chris Wilson 2021-06-17 64 cf586021642d80 Chris Wilson 2021-06-17 65 vaddr = i915_gem_object_pin_map(src, I915_MAP_WC); cf586021642d80 Chris Wilson 2021-06-17 66 if (IS_ERR(vaddr)) { cf586021642d80 Chris Wilson 2021-06-17 67 err = PTR_ERR(vaddr); cf586021642d80 Chris Wilson 2021-06-17 68 continue; cf586021642d80 Chris Wilson 2021-06-17 69 } cf586021642d80 Chris Wilson 2021-06-17 70 cf586021642d80 Chris Wilson 2021-06-17 71 for (i = 0; i < sz / sizeof(u32); i++) cf586021642d80 Chris Wilson 2021-06-17 72 vaddr[i] = i; cf586021642d80 Chris Wilson 2021-06-17 73 i915_gem_object_flush_map(src); cf586021642d80 Chris Wilson 2021-06-17 74 cf586021642d80 Chris Wilson 2021-06-17 75 vaddr = i915_gem_object_pin_map(dst, I915_MAP_WC); cf586021642d80 Chris Wilson 2021-06-17 76 if (IS_ERR(vaddr)) { cf586021642d80 Chris Wilson 2021-06-17 77 err = PTR_ERR(vaddr); cf586021642d80 Chris Wilson 2021-06-17 78 goto unpin_src; cf586021642d80 Chris Wilson 2021-06-17 79 } cf586021642d80 Chris Wilson 2021-06-17 80 cf586021642d80 Chris Wilson 2021-06-17 81 for (i = 0; i < sz / sizeof(u32); i++) cf586021642d80 Chris Wilson 2021-06-17 82 vaddr[i] = ~i; cf586021642d80 Chris Wilson 2021-06-17 83 i915_gem_object_flush_map(dst); cf586021642d80 Chris Wilson 2021-06-17 84 cf586021642d80 Chris Wilson 2021-06-17 85 err = fn(migrate, &ww, src, dst, &rq); cf586021642d80 Chris Wilson 2021-06-17 86 if (!err) cf586021642d80 Chris Wilson 2021-06-17 87 continue;
Does fn() initialize "rq" on the success path? Anyway Smatch would complain anyway because it thinks the list could be empty or that we might hit and early continue for everything.
cf586021642d80 Chris Wilson 2021-06-17 88 cf586021642d80 Chris Wilson 2021-06-17 89 if (err != -EDEADLK && err != -EINTR && err != -ERESTARTSYS) cf586021642d80 Chris Wilson 2021-06-17 90 pr_err("%ps failed, size: %u\n", fn, sz); cf586021642d80 Chris Wilson 2021-06-17 91 if (rq) { cf586021642d80 Chris Wilson 2021-06-17 92 i915_request_wait(rq, 0, HZ); cf586021642d80 Chris Wilson 2021-06-17 93 i915_request_put(rq); cf586021642d80 Chris Wilson 2021-06-17 94 } cf586021642d80 Chris Wilson 2021-06-17 95 i915_gem_object_unpin_map(dst); cf586021642d80 Chris Wilson 2021-06-17 96 unpin_src: cf586021642d80 Chris Wilson 2021-06-17 97 i915_gem_object_unpin_map(src); cf586021642d80 Chris Wilson 2021-06-17 98 } cf586021642d80 Chris Wilson 2021-06-17 99 if (err) cf586021642d80 Chris Wilson 2021-06-17 100 goto err_out; cf586021642d80 Chris Wilson 2021-06-17 101 cf586021642d80 Chris Wilson 2021-06-17 @102 if (rq) { cf586021642d80 Chris Wilson 2021-06-17 103 if (i915_request_wait(rq, 0, HZ) < 0) { cf586021642d80 Chris Wilson 2021-06-17 104 pr_err("%ps timed out, size: %u\n", fn, sz); cf586021642d80 Chris Wilson 2021-06-17 105 err = -ETIME; cf586021642d80 Chris Wilson 2021-06-17 106 } cf586021642d80 Chris Wilson 2021-06-17 107 i915_request_put(rq); cf586021642d80 Chris Wilson 2021-06-17 108 } cf586021642d80 Chris Wilson 2021-06-17 109 cf586021642d80 Chris Wilson 2021-06-17 110 for (i = 0; !err && i < sz / PAGE_SIZE; i++) { cf586021642d80 Chris Wilson 2021-06-17 111 int x = i * 1024 + i915_prandom_u32_max_state(1024, prng); cf586021642d80 Chris Wilson 2021-06-17 112 cf586021642d80 Chris Wilson 2021-06-17 @113 if (vaddr[x] != x) { cf586021642d80 Chris Wilson 2021-06-17 114 pr_err("%ps failed, size: %u, offset: %zu\n", cf586021642d80 Chris Wilson 2021-06-17 115 fn, sz, x * sizeof(u32)); cf586021642d80 Chris Wilson 2021-06-17 116 igt_hexdump(vaddr + i * 1024, 4096); cf586021642d80 Chris Wilson 2021-06-17 117 err = -EINVAL; cf586021642d80 Chris Wilson 2021-06-17 118 } cf586021642d80 Chris Wilson 2021-06-17 119 } cf586021642d80 Chris Wilson 2021-06-17 120 cf586021642d80 Chris Wilson 2021-06-17 121 i915_gem_object_unpin_map(dst); cf586021642d80 Chris Wilson 2021-06-17 122 i915_gem_object_unpin_map(src); cf586021642d80 Chris Wilson 2021-06-17 123 cf586021642d80 Chris Wilson 2021-06-17 124 err_out: cf586021642d80 Chris Wilson 2021-06-17 125 i915_gem_object_put(dst); cf586021642d80 Chris Wilson 2021-06-17 126 err_free_src: cf586021642d80 Chris Wilson 2021-06-17 127 i915_gem_object_put(src); cf586021642d80 Chris Wilson 2021-06-17 128 cf586021642d80 Chris Wilson 2021-06-17 129 return err; cf586021642d80 Chris Wilson 2021-06-17 130 }
--- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org
On Fri, 2 Jul 2021 at 09:45, Dan Carpenter dan.carpenter@oracle.com wrote:
The fn() will always first initialize the rq to NULL. If it returns success then rq will always be a valid rq. If it returns an err then the rq might be NULL, or a valid rq depending on how far the copy/fn got.
And for_i915_gem_ww() will always run at least once, since ww->loop = true, so this looks like a false positive?
On Fri, Jul 02, 2021 at 11:32:45AM +0100, Matthew Auld wrote:
You don't think i915_gem_object_lock(), i915_gem_object_pin_map() or i915_gem_object_pin_map() can fail?
regards, dan carpenter
On Fri, Jul 02, 2021 at 02:07:27PM +0300, Dan Carpenter wrote:
Btw, I sincerely hope that we will re-enable GCC's uninitialized variable checks. Will GCC be able to verify that this is initialized?
regards, dan carpenter
On Fri, 2 Jul 2021 at 12:14, Dan Carpenter dan.carpenter@oracle.com wrote:
34b07d47dd00 ("drm/i915: Enable -Wuninitialized")
GCC doesn't complain AFAIK.
regards, dan carpenter
On Fri, 2 Jul 2021 at 12:07, Dan Carpenter dan.carpenter@oracle.com wrote:
Yeah, they can totally fail but then we mostly likely just hit the err_out. The for_i915_gem_ww() is a little strange since it's not really looping over anything, it's just about retrying the block if we see -EDEADLK(which involves dropping some locks), if we see any other error then the loop is terminated with ww->loop = false, which then hits the goto err_out.
regards, dan carpenter
On Fri, Jul 02, 2021 at 12:34:33PM +0100, Matthew Auld wrote:
Ah, yeah, you're right. False positive.
I hadn't looked at this code in context (I only had reviewed the email). Now that I've pulled the tree and looked at the code, then I'm sort of surprised that Smatch generates a warning... I will investigate some more. Thanks!
regards, dan carpenter
dri-devel@lists.freedesktop.org
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Dan Carpenter -
Matthew Auld