Remove workaround for lock ordering issue in uvm_pseg_get().

Now that uvm_unmap_detach() no longer grab the KERNEL_LOCK() it should be
safe to call it with the `uvm_pseg_lck' mutex held via uvm_km_valloc_try().

ok jca@, claudio@

diff --git a/sys/uvm/uvm_pager.c b/sys/uvm/uvm_pager.c
index 8d661c6..5b8efcd 100644 (file)
--- a/sys/uvm/uvm_pager.c
+++ b/sys/uvm/uvm_pager.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: uvm_pager.c,v 1.91 2023/08/11 17:53:22 mpi Exp $      */
+/*     $OpenBSD: uvm_pager.c,v 1.92 2024/07/24 12:18:10 mpi Exp $      */
 /*     $NetBSD: uvm_pager.c,v 1.36 2000/11/27 18:26:41 chs Exp $       */
 
 /*
@@ -134,24 +134,6 @@ uvm_pseg_get(int flags)
        int i;
        struct uvm_pseg *pseg;
 
-       /*
-        * XXX Prevent lock ordering issue in uvm_unmap_detach().  A real
-        * fix would be to move the KERNEL_LOCK() out of uvm_unmap_detach().
-        *
-        *  witness_checkorder() at witness_checkorder+0xba0
-        *  __mp_lock() at __mp_lock+0x5f
-        *  uvm_unmap_detach() at uvm_unmap_detach+0xc5
-        *  uvm_map() at uvm_map+0x857
-        *  uvm_km_valloc_try() at uvm_km_valloc_try+0x65
-        *  uvm_pseg_get() at uvm_pseg_get+0x6f
-        *  uvm_pagermapin() at uvm_pagermapin+0x45
-        *  uvn_io() at uvn_io+0xcf
-        *  uvn_get() at uvn_get+0x156
-        *  uvm_fault_lower() at uvm_fault_lower+0x28a
-        *  uvm_fault() at uvm_fault+0x1b3
-        *  upageflttrap() at upageflttrap+0x62
-        */
-       KERNEL_LOCK();
        mtx_enter(&uvm_pseg_lck);
 
 pager_seg_restart:
@@ -178,7 +160,6 @@ pager_seg_restart:
                        if (!UVM_PSEG_INUSE(pseg, i)) {
                                pseg->use |= 1 << i;
                                mtx_leave(&uvm_pseg_lck);
-                               KERNEL_UNLOCK();
                                return pseg->start + i * MAXBSIZE;
                        }
                }
@@ -191,7 +172,6 @@ pager_seg_fail:
        }
 
        mtx_leave(&uvm_pseg_lck);
-       KERNEL_UNLOCK();
        return 0;
 }