5.4-stable review patch. If anyone has any objections, please let me know.
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From: Rik van Riel riel@surriel.com
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@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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- 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;