[merged mm-hotfixes-stable] fs-proc-fix-softlockup-in-__read_vmcore-part-2.patch removed from -mm tree

[merged mm-hotfixes-stable] fs-proc-fix-softlockup-in-__read_vmcore-part-2.patch removed from -mm tree

[Andrew Morton]

The quilt patch titled
     Subject: fs/proc: fix softlockup in __read_vmcore (part 2)
has been removed from the -mm tree.  Its filename was
     fs-proc-fix-softlockup-in-__read_vmcore-part-2.patch

This patch was dropped because it was merged into the mm-hotfixes-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

------------------------------------------------------
From: Rik van Riel <riel@surriel.com>
Subject: fs/proc: fix softlockup in __read_vmcore (part 2)
Date: Fri, 10 Jan 2025 10:28:21 -0500

Since commit 5cbcb62dddf5 ("fs/proc: fix softlockup in __read_vmcore") the
number of softlockups in __read_vmcore at kdump time have gone down, but
they still happen sometimes.

In a memory constrained environment like the kdump image, a softlockup is
not just a harmless message, but it can interfere with things like RCU
freeing memory, causing the crashdump to get stuck.

The second loop in __read_vmcore has a lot more opportunities for natural
sleep points, like scheduling out while waiting for a data write to
happen, but apparently that is not always enough.

Add a cond_resched() to the second loop in __read_vmcore to (hopefully)
get rid of the softlockups.

Link: https://lkml.kernel.org/r/20250110102821.2a37581b@fangorn
Fixes: 5cbcb62dddf5 ("fs/proc: fix softlockup in __read_vmcore")
Signed-off-by: Rik van Riel <riel@surriel.com>
Reported-by: Breno Leitao <leitao@debian.org>
Cc: Baoquan He <bhe@redhat.com>
Cc: Dave Young <dyoung@redhat.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 fs/proc/vmcore.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/fs/proc/vmcore.c~fs-proc-fix-softlockup-in-__read_vmcore-part-2
+++ a/fs/proc/vmcore.c
@@ -404,6 +404,8 @@ static ssize_t __read_vmcore(struct iov_
 			if (!iov_iter_count(iter))
 				return acc;
 		}
+
+		cond_resched();
 	}
 
 	return acc;
_

Patches currently in -mm which might be from riel@surriel.com are

mm-remove-unnecessary-calls-to-lru_add_drain.patch