Re: INFO: rcu detected stall in ext4_write_checks
From: Amir Goldstein <amir73il@gmail.com>
Date: 2019-07-05 15:48:00
Also in:
linux-ext4, lkml
Does the (untested, probably does not even build) patch shown below help? This patch assumes that the kernel was built with CONFIG_PREEMPT=n. And that I found all the tight loops on the do_sendfile() code path.
I *think* you have. FWIW, it would have been nicer for sendfile(2) and copy_file_range(2) if the do_splice_direct() loop was also killable/interruptible. Users may want to back off from asking the kernel to copy/send a huge file. Thanks, Amir.
quoted hunk ↗ jump to hunk
quoted
If this is semi-intended, the only option I see is to disable something in syzkaller: sched_setattr entirely, or drop CAP_SYS_NICE, or ...? Any preference either way?Long-running tight loops in the kernel really should contain cond_resched() or better. Thanx, Paul ------------------------------------------------------------------------diff --git a/fs/splice.c b/fs/splice.c index 25212dcca2df..50aa3286764a 100644 --- a/fs/splice.c +++ b/fs/splice.c@@ -985,6 +985,7 @@ ssize_t splice_direct_to_actor(struct file *in, struct splice_desc *sd, sd->pos = prev_pos + ret; goto out_release; } + cond_resched(); } done: