The patch below does not apply to the 3.10-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@xxxxxxxxxxxxxxx>.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
>From 7e6d72c15ff4cc0c27573901bb05f9eddbd71ed4 Mon Sep 17 00:00:00 2001
From: Marcelo Tosatti <mtosatti@xxxxxxxxxx>
Date: Thu, 20 Jun 2013 18:05:56 -0300
Subject: [PATCH] vgacon.c: add cond reschedule points in vgacon_do_font_op
Booting a 64-vcpu KVM guest, with CONFIG_PREEMPT_VOLUNTARY,
can result in a soft lockup:
BUG: soft lockup - CPU#41 stuck for 67s! [setfont:1505]
RIP: 0010:[<ffffffff812c48da>]
[<ffffffff812c48da>] vgacon_do_font_op.clone.0+0x1ba/0x550
This is due to the 8192 (cmapsz) IO operations taking longer than expected
due to lock contention in QEMU.
Add conditional resched points in between writes allowing other tasks to
execute.
Signed-off-by: Marcelo Tosatti <mtosatti@xxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Dave Airlie <airlied@xxxxxxxxxx>
diff --git a/drivers/video/console/vgacon.c b/drivers/video/console/vgacon.c
index 5855d17d..0dd6d962 100644
--- a/drivers/video/console/vgacon.c
+++ b/drivers/video/console/vgacon.c
@@ -1124,11 +1124,15 @@ static int vgacon_do_font_op(struct vgastate *state,char *arg,int set,int ch512)
if (arg) {
if (set)
- for (i = 0; i < cmapsz; i++)
+ for (i = 0; i < cmapsz; i++) {
vga_writeb(arg[i], charmap + i);
+ cond_resched();
+ }
else
- for (i = 0; i < cmapsz; i++)
+ for (i = 0; i < cmapsz; i++) {
arg[i] = vga_readb(charmap + i);
+ cond_resched();
+ }
/*
* In 512-character mode, the character map is not contiguous if
@@ -1139,11 +1143,15 @@ static int vgacon_do_font_op(struct vgastate *state,char *arg,int set,int ch512)
charmap += 2 * cmapsz;
arg += cmapsz;
if (set)
- for (i = 0; i < cmapsz; i++)
+ for (i = 0; i < cmapsz; i++) {
vga_writeb(arg[i], charmap + i);
+ cond_resched();
+ }
else
- for (i = 0; i < cmapsz; i++)
+ for (i = 0; i < cmapsz; i++) {
arg[i] = vga_readb(charmap + i);
+ cond_resched();
+ }
}
}
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