mtd_blkdevs: avoid soft lockups with some mtd/spi devices

From: David Decotigny <[email protected]>

With some spi devices, the heavy cpu usage due to polling the spi registers may lead to netdev timeouts, RCU complaints, etc. This can be acute in the absence of CONFIG_PREEMPT. This patch allows to give enough breathing room to avoid those false positives.

---

I tested this on a 5.10 base (lockdep).

 drivers/mtd/mtd_blkdevs.c | 1 +
 1 file changed, 1 insertion(+)

index 243f28a3206b4..64d2b093f114b 100644
@@ -158,6 +158,7 @@ static void mtd_blktrans_work(struct mtd_blktrans_dev *dev)
 		}
 
 		background_done = 0;
+		cond_resched();
 		spin_lock_irq(&dev->queue_lock);
 	}
 }

2.35.0.rc0.227.g00780c9af4-goog

David,

----- Ursprüngliche Mail -----

is the problem real or not? From your description it is not clear to me. Please include lockdep splats and/or hung-task logs in the commit message.

I have no problem with adding a cond_resched() but first we need to understand the issue a little better.

Thanks,
//richard

----- Ursprüngliche Mail -----

Okay. But then it isn't a false positive as you write in the commit message.

Thanks,
//richard