Am 27.02.25 um 13:52 schrieb Andi Shyti: > Hi Nitin, > > On Wed, Feb 26, 2025 at 09:25:34PM +0530, Nitin Gote wrote: >> Give the scheduler a chance to breath by calling cond_resched() >> as some of the loops may take some time on old machines (like apl/bsw/pnv), >> and so catch the attention of the watchdogs. >> >> Closes: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/12904 >> Signed-off-by: Nitin Gote <nitin.r.gote@xxxxxxxxx> > This patch goes beyond the intel-gfx domain so that you need to > add some people in Cc. By running checkpatch, you should add: > > Sumit Semwal <sumit.semwal@xxxxxxxxxx> (maintainer:DMA BUFFER SHARING FRAMEWORK) > "Christian König" <christian.koenig@xxxxxxx> (maintainer:DMA BUFFER SHARING FRAMEWORK) > linux-media@xxxxxxxxxxxxxxx (open list:DMA BUFFER SHARING FRAMEWORK) > dri-devel@xxxxxxxxxxxxxxxxxxxxx (open list:DMA BUFFER SHARING FRAMEWORK) > > I added them now, but you might still be asked to resend. > > Said that, at a first glance, I don't have anything against this > patch. There has been some push to deprecate cond_resched() cause it is almost always not appropriate. Saying that if I'm not completely mistaken that here is also not 100% correct usage. Question is why is the test taking 26 (busy?) seconds to complete? That sounds really long even for a very old CPU. Do we maybe have an udelay() here which should have been an usleep() or similar? Regards, Christian. > > Andi > >> --- >> Hi, >> >> For reviewer reference, adding here watchdog issue seen on old machines >> during dma-fence-chain subtests testing. This log is retrieved from device >> pstore log while testing dam-buf@all-tests: >> >> dma-buf: Running dma_fence_chain >> Panic#1 Part7 >> <6> sizeof(dma_fence_chain)=184 >> <6> dma-buf: Running dma_fence_chain/sanitycheck >> <6> dma-buf: Running dma_fence_chain/find_seqno >> <6> dma-buf: Running dma_fence_chain/find_signaled >> <6> dma-buf: Running dma_fence_chain/find_out_of_order >> <6> dma-buf: Running dma_fence_chain/find_gap >> <6> dma-buf: Running dma_fence_chain/find_race >> <6> Completed 4095 cycles >> <6> dma-buf: Running dma_fence_chain/signal_forward >> <6> dma-buf: Running dma_fence_chain/signal_backward >> <6> dma-buf: Running dma_fence_chain/wait_forward >> <6> dma-buf: Running dma_fence_chain/wait_backward >> <0> watchdog: BUG: soft lockup - CPU#2 stuck for 26s! [dmabuf:2263] >> Panic#1 Part6 >> <4> irq event stamp: 415735 >> <4> hardirqs last enabled at (415734): [<ffffffff813d3a1b>] handle_softirqs+0xab/0x4d0 >> <4> hardirqs last disabled at (415735): [<ffffffff827c7e31>] sysvec_apic_timer_interrupt+0x11/0xc0 >> <4> softirqs last enabled at (415728): [<ffffffff813d3f8f>] __irq_exit_rcu+0x13f/0x160 >> <4> softirqs last disabled at (415733): [<ffffffff813d3f8f>] __irq_exit_rcu+0x13f/0x160 >> <4> CPU: 2 UID: 0 PID: 2263 Comm: dmabuf Not tainted 6.14.0-rc2-drm-next_483-g7b91683e7de7+ #1 >> <4> Hardware name: Intel corporation NUC6CAYS/NUC6CAYB, BIOS AYAPLCEL.86A.0056.2018.0926.1100 09/26/2018 >> <4> RIP: 0010:handle_softirqs+0xb1/0x4d0 >> <4> RSP: 0018:ffffc90000154f60 EFLAGS: 00000246 >> <4> RAX: 0000000000000000 RBX: 0000000000000001 RCX: 0000000000000000 >> <4> RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000 >> <4> RBP: ffffc90000154fb8 R08: 0000000000000000 R09: 0000000000000000 >> <4> R10: 0000000000000000 R11: 0000000000000000 R12: 000000000000000a >> <4> R13: 0000000000000200 R14: 0000000000000200 R15: 0000000000400100 >> <4> FS: 000077521c5cd940(0000) GS:ffff888277900000(0000) knlGS:0000000000000000 >> Panic#1 Part5 >> <4> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 >> <4> CR2: 00005dbfee8c00c4 CR3: 0000000133d38000 CR4: 00000000003526f0 >> <4> Call Trace: >> <4> <IRQ> >> <4> ? show_regs+0x6c/0x80 >> <4> ? watchdog_timer_fn+0x247/0x2d0 >> <4> ? __pfx_watchdog_timer_fn+0x10/0x10 >> <4> ? __hrtimer_run_queues+0x1d0/0x420 >> <4> ? hrtimer_interrupt+0x116/0x290 >> <4> ? __sysvec_apic_timer_interrupt+0x70/0x1e0 >> <4> ? sysvec_apic_timer_interrupt+0x47/0xc0 >> <4> ? asm_sysvec_apic_timer_interrupt+0x1b/0x20 >> <4> ? handle_softirqs+0xb1/0x4d0 >> <4> __irq_exit_rcu+0x13f/0x160 >> <4> irq_exit_rcu+0xe/0x20 >> <4> sysvec_irq_work+0xa0/0xc0 >> <4> </IRQ> >> <4> <TASK> >> <4> asm_sysvec_irq_work+0x1b/0x20 >> <4> RIP: 0010:_raw_spin_unlock_irqrestore+0x57/0x80 >> <4> RSP: 0018:ffffc9000292b8f0 EFLAGS: 00000246 >> <4> RAX: 0000000000000000 RBX: ffff88810f235480 RCX: 0000000000000000 >> <4> RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000 >> <4> RBP: ffffc9000292b900 R08: 0000000000000000 R09: 0000000000000000 >> <4> R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000246 >> <4> R13: 0000000000000000 R14: 0000000000000246 R15: 000000000003828c >> Panic#1 Part4 >> <4> dma_fence_signal+0x49/0xb0 >> <4> wait_backward+0xf8/0x140 [dmabuf_selftests] >> <4> __subtests+0x75/0x1f0 [dmabuf_selftests] >> <4> dma_fence_chain+0x94/0xe0 [dmabuf_selftests] >> <4> st_init+0x6a/0xff0 [dmabuf_selftests] >> <4> ? __pfx_st_init+0x10/0x10 [dmabuf_selftests] >> <4> do_one_initcall+0x79/0x400 >> <4> do_init_module+0x97/0x2a0 >> <4> load_module+0x2c23/0x2f60 >> <4> init_module_from_file+0x97/0xe0 >> <4> ? init_module_from_file+0x97/0xe0 >> <4> idempotent_init_module+0x134/0x350 >> <4> __x64_sys_finit_module+0x77/0x100 >> <4> x64_sys_call+0x1f37/0x2650 >> <4> do_syscall_64+0x91/0x180 >> <4> ? trace_hardirqs_off+0x5d/0xe0 >> <4> ? syscall_exit_to_user_mode+0x95/0x260 >> <4> ? do_syscall_64+0x9d/0x180 >> <4> ? do_syscall_64+0x9d/0x180 >> <4> ? irqentry_exit+0x77/0xb0 >> <4> ? sysvec_apic_timer_interrupt+0x57/0xc0 >> <4> entry_SYSCALL_64_after_hwframe+0x76/0x7e >> <4> RIP: 0033:0x77521e72725d >> >> >> drivers/dma-buf/st-dma-fence-chain.c | 14 +++++++++++--- >> 1 file changed, 11 insertions(+), 3 deletions(-) >> >> diff --git a/drivers/dma-buf/st-dma-fence-chain.c b/drivers/dma-buf/st-dma-fence-chain.c >> index ed4b323886e4..328a66ed59e5 100644 >> --- a/drivers/dma-buf/st-dma-fence-chain.c >> +++ b/drivers/dma-buf/st-dma-fence-chain.c >> @@ -505,6 +505,7 @@ static int signal_forward(void *arg) >> >> for (i = 0; i < fc.chain_length; i++) { >> dma_fence_signal(fc.fences[i]); >> + cond_resched(); >> >> if (!dma_fence_is_signaled(fc.chains[i])) { >> pr_err("chain[%d] not signaled!\n", i); >> @@ -537,6 +538,7 @@ static int signal_backward(void *arg) >> >> for (i = fc.chain_length; i--; ) { >> dma_fence_signal(fc.fences[i]); >> + cond_resched(); >> >> if (i > 0 && dma_fence_is_signaled(fc.chains[i])) { >> pr_err("chain[%d] is signaled!\n", i); >> @@ -587,8 +589,10 @@ static int wait_forward(void *arg) >> get_task_struct(tsk); >> yield_to(tsk, true); >> >> - for (i = 0; i < fc.chain_length; i++) >> + for (i = 0; i < fc.chain_length; i++) { >> dma_fence_signal(fc.fences[i]); >> + cond_resched(); >> + } >> >> err = kthread_stop_put(tsk); >> >> @@ -616,8 +620,10 @@ static int wait_backward(void *arg) >> get_task_struct(tsk); >> yield_to(tsk, true); >> >> - for (i = fc.chain_length; i--; ) >> + for (i = fc.chain_length; i--; ) { >> dma_fence_signal(fc.fences[i]); >> + cond_resched(); >> + } >> >> err = kthread_stop_put(tsk); >> >> @@ -663,8 +669,10 @@ static int wait_random(void *arg) >> get_task_struct(tsk); >> yield_to(tsk, true); >> >> - for (i = 0; i < fc.chain_length; i++) >> + for (i = 0; i < fc.chain_length; i++) { >> dma_fence_signal(fc.fences[i]); >> + cond_resched(); >> + } >> >> err = kthread_stop_put(tsk); >> >> -- >> 2.25.1
