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authorMarcelo Tosatti <mtosatti@redhat.com>2013-06-20 18:05:56 -0300
committerDave Airlie <airlied@redhat.com>2013-06-26 16:27:55 +1000
commit7e6d72c15ff4cc0c27573901bb05f9eddbd71ed4 (patch)
treeb9a2ea68e5455051856b3bf6693cd548d435a0ec /drivers/video/console
parent5cef29aa5227e6347145940a7bccde92fd9a1afa (diff)
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@redhat.com> Cc: stable@vger.kernel.org Signed-off-by: Dave Airlie <airlied@redhat.com>
Diffstat (limited to 'drivers/video/console')
-rw-r--r--drivers/video/console/vgacon.c16
1 files changed, 12 insertions, 4 deletions
diff --git a/drivers/video/console/vgacon.c b/drivers/video/console/vgacon.c
index 5855d17d19ac..0dd6d9625bb5 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();
+ }
}
}