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Date: Sat, 23 Oct 2021 08:59:32 -0700
From: Rob Clark <robdclark@...il.com>
To: Jessica Zhang <jesszhan@...eaurora.org>
Cc: dri-devel <dri-devel@...ts.freedesktop.org>,
freedreno <freedreno@...ts.freedesktop.org>,
linux-arm-msm <linux-arm-msm@...r.kernel.org>,
Rob Clark <robdclark@...omium.org>,
Sean Paul <sean@...rly.run>, David Airlie <airlied@...ux.ie>,
Daniel Vetter <daniel@...ll.ch>,
Thomas Zimmermann <tzimmermann@...e.de>,
Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
Maxime Ripard <maxime@...no.tech>,
Abhinav Kumar <abhinavk@...eaurora.org>,
Stephen Boyd <swboyd@...omium.org>,
Krishna Manikandan <mkrishn@...eaurora.org>,
Kalyan Thota <kalyan_t@...eaurora.org>,
Mark Yacoub <markyacoub@...gle.com>,
open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] drm/msm/dpu: Remove dynamic allocation from atomic context
On Fri, Oct 22, 2021 at 12:15 PM Jessica Zhang <jesszhan@...eaurora.org> wrote:
>
> On 10/22/2021 10:20 AM, Rob Clark wrote:
> > From: Rob Clark <robdclark@...omium.org>
> >
> > We know the upper bound on # of mixers (ie. two), so lets just allocate
> > this on the stack.
> >
> > Fixes:
> >
> > BUG: sleeping function called from invalid context at include/linux/sched/mm.h:201
> > in_atomic(): 1, irqs_disabled(): 128, non_block: 0, pid: 0, name: swapper/0
> > INFO: lockdep is turned off.
> > irq event stamp: 43642
> > hardirqs last enabled at (43641): [<ffffffe24dd276bc>] cpuidle_enter_state+0x158/0x25c
> > hardirqs last disabled at (43642): [<ffffffe24dfff450>] enter_el1_irq_or_nmi+0x10/0x1c
> > softirqs last enabled at (43620): [<ffffffe24d4103fc>] __do_softirq+0x1e4/0x464
> > softirqs last disabled at (43615): [<ffffffe24d48bd90>] __irq_exit_rcu+0x104/0x150
> > CPU: 0 PID: 0 Comm: swapper/0 Tainted: G W 5.15.0-rc3-debug+ #105
> > Hardware name: Google Lazor (rev1 - 2) with LTE (DT)
> > Call trace:
> > dump_backtrace+0x0/0x18c
> > show_stack+0x24/0x30
> > dump_stack_lvl+0xa0/0xd4
> > dump_stack+0x18/0x34
> > ___might_sleep+0x1e0/0x1f0
> > __might_sleep+0x78/0x8c
> > slab_pre_alloc_hook.constprop.0+0x48/0x6c
> > __kmalloc+0xc8/0x21c
> > dpu_crtc_vblank_callback+0x158/0x1f8
> > dpu_encoder_vblank_callback+0x70/0xc4
> > dpu_encoder_phys_vid_vblank_irq+0x50/0x12c
> > dpu_core_irq+0x1bc/0x1d0
> > dpu_irq+0x1c/0x28
> > msm_irq+0x34/0x40
> > __handle_irq_event_percpu+0x15c/0x308
> > handle_irq_event_percpu+0x3c/0x90
> > handle_irq_event+0x54/0x98
> > handle_level_irq+0xa0/0xd0
> > handle_irq_desc+0x2c/0x44
> > generic_handle_domain_irq+0x28/0x34
> > dpu_mdss_irq+0x90/0xe8
> > handle_irq_desc+0x2c/0x44
> > handle_domain_irq+0x54/0x80
> > gic_handle_irq+0xd4/0x148
> > call_on_irq_stack+0x2c/0x54
> > do_interrupt_handler+0x4c/0x64
> > el1_interrupt+0x30/0xd0
> > el1h_64_irq_handler+0x18/0x24
> > el1h_64_irq+0x78/0x7c
> > arch_local_irq_enable+0xc/0x14
> > cpuidle_enter+0x44/0x5c
> > do_idle+0x248/0x268
> > cpu_startup_entry+0x30/0x48
> > rest_init+0x188/0x19c
> > arch_call_rest_init+0x1c/0x28
> > start_kernel+0x704/0x744
> > __primary_switched+0xc0/0xc8
> >
> > Fixes: 78d9b458cc21 ("drm/msm/dpu: Add CRC support for DPU")
> > Signed-off-by: Rob Clark <robdclark@...omium.org>
> > ---
> > drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c | 16 +++++-----------
> > 1 file changed, 5 insertions(+), 11 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
> > index 0ae397044310..80c0ae688734 100644
> > --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
> > +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
> > @@ -182,21 +182,19 @@ static int dpu_crtc_get_crc(struct drm_crtc *crtc)
> > {
> > struct dpu_crtc_state *crtc_state;
> > struct dpu_crtc_mixer *m;
> > - u32 *crcs;
> > + u32 crcs[CRTC_DUAL_MIXERS];
> >
> > int i = 0;
> > int rc = 0;
> >
> > crtc_state = to_dpu_crtc_state(crtc->state);
> > - crcs = kcalloc(crtc_state->num_mixers, sizeof(*crcs), GFP_KERNEL);
> >
> > - if (!crcs)
> > - return -ENOMEM;
> > + static_assert(ARRAY_SIZE(crcs) == ARRAY_SIZE(crtc_state->mixers));
> >
>
> Getting a C90 compiler warning for static_assert():
>
> In file included from ./include/linux/bits.h:22,
> from ./include/linux/bitops.h:6,
> from ./include/linux/kernel.h:12,
> from ./include/linux/list.h:9,
> from ./include/linux/wait.h:7,
> from ./include/linux/wait_bit.h:8,
> from ./include/linux/fs.h:6,
> from ./include/linux/debugfs.h:15,
> from drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c:10:
> drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c: In function
> ‘dpu_crtc_get_crc’:
> ./include/linux/build_bug.h:78:41: warning: ISO C90 forbids mixed
> declarations and code [-Wdeclaration-after-statement]
> 78 | #define __static_assert(expr, msg, ...)
> _Static_assert(expr, msg)
> | ^~~~~~~~~~~~~~
> ./include/linux/build_bug.h:77:34: note: in expansion of macro
> ‘__static_assert’
> 77 | #define static_assert(expr, ...) __static_assert(expr,
> ##__VA_ARGS__, #expr)
> | ^~~~~~~~~~~~~~~
> drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c:192:2: note: in expansion
> of macro ‘static_assert’
> 192 | static_assert(ARRAY_SIZE(crcs) ==
> ARRAY_SIZE(crtc_state->mixers));
> | ^~~~~~~~~~~~~
>
> Can be fixed by moving the static_assert() before `crtc_state = ...`
>
I was trying to avoid moving that because I've seen tools flag things
like that as use-before-init before. But I guess I can use
BUILD_BUG_ON() instead.
BR,
-R
> Thanks,
>
> Jessica Zhang
>
> > /* Skip first 2 frames in case of "uncooked" CRCs */
> > if (crtc_state->crc_frame_skip_count < 2) {
> > crtc_state->crc_frame_skip_count++;
> > - goto cleanup;
> > + return 0;
> > }
> >
> > for (i = 0; i < crtc_state->num_mixers; ++i) {
> > @@ -210,16 +208,12 @@ static int dpu_crtc_get_crc(struct drm_crtc *crtc)
> >
> > if (rc) {
> > DRM_DEBUG_DRIVER("MISR read failed\n");
> > - goto cleanup;
> > + return rc;
> > }
> > }
> >
> > - rc = drm_crtc_add_crc_entry(crtc, true,
> > + return drm_crtc_add_crc_entry(crtc, true,
> > drm_crtc_accurate_vblank_count(crtc), crcs);
> > -
> > -cleanup:
> > - kfree(crcs);
> > - return rc;
> > }
> >
> > static bool dpu_crtc_get_scanout_position(struct drm_crtc *crtc,
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