From 7e6d72c15ff4cc0c27573901bb05f9eddbd71ed4 Mon Sep 17 00:00:00 2001 From: Marcelo Tosatti Date: Thu, 20 Jun 2013 18:05:56 -0300 Subject: 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:[] [] 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 Cc: stable@vger.kernel.org Signed-off-by: Dave Airlie --- drivers/video/console/vgacon.c | 16 ++++++++++++---- 1 file changed, 12 insertions(+), 4 deletions(-) (limited to 'drivers/video/console') 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(); + } } } -- cgit v1.2.3 From 0ab3691fa8ac15ed94f9e2fa7c2958ab41d2e3f5 Mon Sep 17 00:00:00 2001 From: Dave Airlie Date: Thu, 27 Jun 2013 10:07:39 +1000 Subject: vgacon: fix missing include. This fixes the build error. Signed-off-by: Dave Airlie --- drivers/video/console/vgacon.c | 1 + 1 file changed, 1 insertion(+) (limited to 'drivers/video/console') diff --git a/drivers/video/console/vgacon.c b/drivers/video/console/vgacon.c index 0dd6d9625bb5..9d8feac67637 100644 --- a/drivers/video/console/vgacon.c +++ b/drivers/video/console/vgacon.c @@ -42,6 +42,7 @@ #include #include #include +#include #include #include #include -- cgit v1.2.3