5.4-stable review patch. If anyone has any objections, please let me know.
------------------
From: Rik van Riel <riel@xxxxxxxxxxx>
commit cbc5dde0a461240046e8a41c43d7c3b76d5db952 upstream.
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@xxxxxxxxxxx>
Reported-by: Breno Leitao <leitao@xxxxxxxxxx>
Cc: Baoquan He <bhe@xxxxxxxxxx>
Cc: Dave Young <dyoung@xxxxxxxxxx>
Cc: Vivek Goyal <vgoyal@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/proc/vmcore.c | 2 ++
1 file changed, 2 insertions(+)
--- a/fs/proc/vmcore.c
+++ b/fs/proc/vmcore.c
@@ -397,6 +397,8 @@ static ssize_t __read_vmcore(char *buffe
if (buflen == 0)
return acc;
}
+
+ cond_resched();
}
return acc;
