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fs/proc: fix softlockup in __read_vmcore (part 2)

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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>
This commit is contained in:
Rik van Riel 2025-01-10 10:28:21 -05:00 committed by Andrew Morton
parent 1c47c57818
commit cbc5dde0a4
1 changed files with 2 additions and 0 deletions
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2
fs/proc/vmcore.c
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@ -404,6 +404,8 @@ static ssize_t __read_vmcore(struct iov_iter *iter, loff_t *fpos)
if (!iov_iter_count(iter)) if (!iov_iter_count(iter))
return acc; return acc;
} }
cond_resched();
} }
return acc; return acc;