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>
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@ -1124,11 +1124,15 @@ static int vgacon_do_font_op(struct vgastate *state,char *arg,int set,int ch512)
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if (arg) {
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if (set)
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for (i = 0; i < cmapsz; i++)
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for (i = 0; i < cmapsz; i++) {
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vga_writeb(arg[i], charmap + i);
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cond_resched();
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}
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else
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for (i = 0; i < cmapsz; i++)
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for (i = 0; i < cmapsz; i++) {
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arg[i] = vga_readb(charmap + i);
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cond_resched();
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}
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/*
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* In 512-character mode, the character map is not contiguous if
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@ -1139,11 +1143,15 @@ static int vgacon_do_font_op(struct vgastate *state,char *arg,int set,int ch512)
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charmap += 2 * cmapsz;
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arg += cmapsz;
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if (set)
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for (i = 0; i < cmapsz; i++)
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for (i = 0; i < cmapsz; i++) {
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vga_writeb(arg[i], charmap + i);
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cond_resched();
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}
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else
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for (i = 0; i < cmapsz; i++)
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for (i = 0; i < cmapsz; i++) {
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arg[i] = vga_readb(charmap + i);
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cond_resched();
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}
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}
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}
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