MFC 303076,303225: Use MTX_SYSINIT for the VESA lock.

303076:
vesa: fix panic on suspend

Fix the following panic seen when migrating a FreeBSD guest on Xen:

panic: mtx_lock() of destroyed mutex @ /usr/src/sys/dev/fb/vesa.c:541
cpuid = 0
KDB: stack backtrace:
db_trace_self_wrapper() at db_trace_self_wrapper+0x2b/frame 0xfffffe001d2fa4f0
vpanic() at vpanic+0x182/frame 0xfffffe001d2fa570
kassert_panic() at kassert_panic+0x126/frame 0xfffffe001d2fa5e0
__mtx_lock_flags() at __mtx_lock_flags+0x15b/frame 0xfffffe001d2fa630
vesa_bios_save_restore() at vesa_bios_save_restore+0x78/frame 0xfffffe001d2fa680
vga_suspend() at vga_suspend+0xa3/frame 0xfffffe001d2fa6b0
isavga_suspend() at isavga_suspend+0x1d/frame 0xfffffe001d2fa6d0
bus_generic_suspend_child() at bus_generic_suspend_child+0x44/frame
[...]

This is caused because vga_sub_configure (which is called if the VGA adapter
is attached after VESA tried to initialize), points to vesa_configure, which
doesn't initialize the VESA mutex. In order to fix it, make sure
vga_sub_configure points to vesa_load, so that all the needed vesa
components are properly initialized.

303225:
Use MTX_SYSINIT for the VESA lock.

vesa_init_done isn't a reliable guard for the mutex init.  If
vesa_configure() doesn't find valid VESA info it will not set
vesa_init_done, but the lock will remain initialized.  Revert r303076
and use MTX_SYSINIT to deterministically init the lock.

PR:		209203

1 files changed, 1 insertions, 3 deletions

diff --git a/sys/dev/fb/vesa.c b/sys/dev/fb/vesa.c
index 1db24bd..bd4b261 100644
--- a/sys/dev/fb/vesa.c
+++ b/sys/dev/fb/vesa.c
@@ -79,6 +79,7 @@ struct adp_state {
 typedef struct adp_state adp_state_t;
 
 static struct mtx vesa_lock;
+MTX_SYSINIT(vesa_lock, &vesa_lock, "VESA lock", MTX_DEF);
 
 static int vesa_state;
 static void *vesa_state_buf;
@@ -1915,8 +1916,6 @@ vesa_load(void)
 	if (vesa_init_done)
 		return (0);
 
-	mtx_init(&vesa_lock, "VESA lock", NULL, MTX_DEF);
-
 	/* locate a VGA adapter */
 	vesa_adp = NULL;
 	error = vesa_configure(0);
@@ -1955,7 +1954,6 @@ vesa_unload(void)
 	}
 
 	vesa_bios_uninit();
-	mtx_destroy(&vesa_lock);
 
 	return (error);
 }