The patch titled Subject: fs/proc: fix softlockup in __read_vmcore (part 2) has been added to the -mm mm-hotfixes-unstable branch. Its filename is fs-proc-fix-softlockup-in-__read_vmcore-part-2.patch
This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches...
This patch will later appear in the mm-hotfixes-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------ 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
fs-proc-fix-softlockup-in-__read_vmcore-part-2.patch mm-remove-unnecessary-calls-to-lru_add_drain.patch