Am 18.03.25 um 11:34 schrieb Nitin Gote: > Give the scheduler a chance to breathe by calling cond_resched() > as some of the loops may take some time on old machines (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> > --- > Cc: Christian Konig <christian.koenig@xxxxxxx> > > Hi Konig, > > This is not a functional issue in test. Exactly that doesn't sounds correct to me. > We wish to prevent softlock and allow the > dma-fence-chain test run to completion to verify it's functional correctness. > > The performance issue takes about 5ms for the dma-fence-chain to be signalled on > older hardware which is an orthogonal issue and to be debugged separately for > which the test has to run to completion. > > So, reverting to cond_resched() which fixes the issue instead of > delay functions. See what the warning is all about is that the CPU *busy* on something for more than 26seconds. Even on older hardware that should absolutely not happen. So what we either have is a bug in the test case (perfectly possible) or we have a bug in the dma-fence-chain implementation. As long as you don't come with a good explanation why the test case keeps the CPU busy for that long this patch here is a clear NAK from my side. Regards, Christian. > > - Nitin > > 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); >
