mutex(9): initialize some more mutexes before use?

[Patrick Wildt]

Hi,

I was playing around a little with the mutex code and found that on
arm64 there some uninitialized mutexes out there.

I think the arm64 specific one is comparatively easy to solve.  We
either initialize the mtx when we initialize the rest of the pmap, or
we move it into the global definition of those.  I opted for the former
version.

The other one prolly needs more discussion/debugging.  So uvm_init()
calls first pmap_init() and then uvm_km_page_init().  The latter does
initialize the mutex, but arm64's pmap_init() already uses pools, which
uses km_alloc, which then uses that mutex.  Now one easy fix would be
to just initialize the definition right away instead of during runtime.

But there might be the question if arm64's pmap is allowed to use pools
and km_alloc during pmap_init.

Patrick

#0  0xffffff800073f984 in mtx_enter (mtx=0xffffff8000f3b048 <uvm_km_pages>) at 
/usr/src/sys/kern/kern_lock.c:281
#1  0xffffff8000937e6c in km_alloc (sz=<error reading variable: Unhandled dwarf 
expression opcode 0xa3>, kv=0xffffff8000da6a30 <kv_page>, kp=0xffffff8000da6a48 
<kp_dirty>, kd=0xffffff8000e934d8)
    at /usr/src/sys/uvm/uvm_km.c:899
#2  0xffffff800084d804 in pool_page_alloc (pp=<error reading variable: 
Unhandled dwarf expression opcode 0xa3>, flags=<error reading variable: 
Unhandled dwarf expression opcode 0xa3>,
    slowdown=<error reading variable: Unhandled dwarf expression opcode 0xa3>) 
at /usr/src/sys/kern/subr_pool.c:1633
#3  0xffffff800084f8dc in pool_allocator_alloc (pp=0xffffff8000ea6e40 
<pmap_pmap_pool>, flags=65792, slowdown=0xffffff80026cd098) at 
/usr/src/sys/kern/subr_pool.c:1602
#4  0xffffff800084ef08 in pool_p_alloc (pp=0xffffff8000ea6e40 <pmap_pmap_pool>, 
flags=2, slowdown=0xffffff8000e9359c) at /usr/src/sys/kern/subr_pool.c:926
#5  0xffffff800084f808 in pool_prime (pp=<optimized out>, n=<error reading 
variable: Unhandled dwarf expression opcode 0xa3>) at 
/usr/src/sys/kern/subr_pool.c:896
#6  0xffffff800048c20c in pmap_init () at 
/usr/src/sys/arch/arm64/arm64/pmap.c:1682
#7  0xffffff80009384dc in uvm_init () at /usr/src/sys/uvm/uvm_init.c:118
#8  0xffffff800048e664 in main (framep=<error reading variable: Unhandled dwarf 
expression opcode 0xa3>) at /usr/src/sys/kern/init_main.c:235

diff --git a/sys/arch/arm64/arm64/pmap.c b/sys/arch/arm64/arm64/pmap.c
index 79a344cc84e..f070f4540ec 100644
--- a/sys/arch/arm64/arm64/pmap.c
+++ b/sys/arch/arm64/arm64/pmap.c
@@ -1308,10 +1308,12 @@ pmap_bootstrap(long kvo, paddr_t lpt1, long 
kernelstart, long kernelend,
        pmap_kernel()->pm_vp.l1 = (struct pmapvp1 *)va;
        pmap_kernel()->pm_privileged = 1;
        pmap_kernel()->pm_asid = 0;
+       mtx_init(&pmap_kernel()->pm_mtx, IPL_VM);
 
        pmap_tramp.pm_vp.l1 = (struct pmapvp1 *)va + 1;
        pmap_tramp.pm_privileged = 1;
        pmap_tramp.pm_asid = 0;
+       mtx_init(&pmap_tramp.pm_mtx, IPL_VM);
 
        /* Mark ASID 0 as in-use. */
        pmap_asid[0] |= (3U << 0);
diff --git a/sys/uvm/uvm_km.c b/sys/uvm/uvm_km.c
index 4a60377e9d7..e77afeda832 100644
--- a/sys/uvm/uvm_km.c
+++ b/sys/uvm/uvm_km.c
@@ -644,7 +644,7 @@ uvm_km_page_lateinit(void)
  * not zero filled.
  */
 
-struct uvm_km_pages uvm_km_pages;
+struct uvm_km_pages uvm_km_pages = { .mtx = MUTEX_INITIALIZER(IPL_VM) };
 
 void uvm_km_createthread(void *);
 void uvm_km_thread(void *);
@@ -664,7 +664,6 @@ uvm_km_page_init(void)
        int     len, bulk;
        vaddr_t addr;
 
-       mtx_init(&uvm_km_pages.mtx, IPL_VM);
        if (!uvm_km_pages.lowat) {
                /* based on physmem, calculate a good value here */
                uvm_km_pages.lowat = physmem / 256;