Do not hold the process around the vm_fault() call from the trap()s.

The only operation which is prevented by the hold is the kernel stack
swapout for the faulted thread, which should be fine to allow.

Remove useless checks for NULL curproc or curproc->p_vmspace from the
trap_pfault() wrappers on x86 and powerpc.

Reviewed by:	alc (previous version)
Sponsored by:	The FreeBSD Foundation
MFC after:	2 weeks

8 files changed, 22 insertions, 198 deletions

diff --git a/sys/amd64/amd64/trap.c b/sys/amd64/amd64/trap.c
index fa74eb2..3bf63c3 100644
--- a/sys/amd64/amd64/trap.c
+++ b/sys/amd64/amd64/trap.c
@@ -625,7 +625,6 @@ trap_pfault(frame, usermode)
 	int usermode;
 {
 	vm_offset_t va;
-	struct vmspace *vm;
 	vm_map_t map;
 	int rv = 0;
 	vm_prot_t ftype;
@@ -687,14 +686,7 @@ trap_pfault(frame, usermode)
 
 		map = kernel_map;
 	} else {
-		/*
-		 * This is a fault on non-kernel virtual memory.  If either
-		 * p or p->p_vmspace is NULL, then the fault is fatal.
-		 */
-		if (p == NULL || (vm = p->p_vmspace) == NULL)
-			goto nogo;
-
-		map = &vm->vm_map;
+		map = &p->p_vmspace->vm_map;
 
 		/*
 		 * When accessing a usermode address, kernel must be
@@ -729,28 +721,8 @@ trap_pfault(frame, usermode)
 	else
 		ftype = VM_PROT_READ;
 
-	if (map != kernel_map) {
-		/*
-		 * Keep swapout from messing with us during this
-		 *	critical time.
-		 */
-		PROC_LOCK(p);
-		++p->p_lock;
-		PROC_UNLOCK(p);
-
-		/* Fault in the user page: */
-		rv = vm_fault(map, va, ftype, VM_FAULT_NORMAL);
-
-		PROC_LOCK(p);
-		--p->p_lock;
-		PROC_UNLOCK(p);
-	} else {
-		/*
-		 * Don't have to worry about process locking or stacks in the
-		 * kernel.
-		 */
-		rv = vm_fault(map, va, ftype, VM_FAULT_NORMAL);
-	}
+	/* Fault in the page. */
+	rv = vm_fault(map, va, ftype, VM_FAULT_NORMAL);
 	if (rv == KERN_SUCCESS) {
 #ifdef HWPMC_HOOKS
 		if (ftype == VM_PROT_READ || ftype == VM_PROT_WRITE) {
diff --git a/sys/arm/arm/trap-v6.c b/sys/arm/arm/trap-v6.c
index 09fc0fc..b7b6629 100644
--- a/sys/arm/arm/trap-v6.c
+++ b/sys/arm/arm/trap-v6.c
@@ -500,28 +500,9 @@ abort_handler(struct trapframe *tf, int prefetch)
 	onfault = pcb->pcb_onfault;
 	pcb->pcb_onfault = NULL;
 #endif
-	if (map != kernel_map) {
-		/*
-		 * Keep swapout from messing with us during this
-		 *	critical time.
-		 */
-		PROC_LOCK(p);
-		++p->p_lock;
-		PROC_UNLOCK(p);
 
-		/* Fault in the user page: */
-		rv = vm_fault(map, va, ftype, VM_FAULT_NORMAL);
-
-		PROC_LOCK(p);
-		--p->p_lock;
-		PROC_UNLOCK(p);
-	} else {
-		/*
-		 * Don't have to worry about process locking or stacks in the
-		 * kernel.
-		 */
-		rv = vm_fault(map, va, ftype, VM_FAULT_NORMAL);
-	}
+	/* Fault in the page. */
+	rv = vm_fault(map, va, ftype, VM_FAULT_NORMAL);
 
 #ifdef INVARIANTS
 	pcb->pcb_onfault = onfault;
diff --git a/sys/arm/arm/trap.c b/sys/arm/arm/trap.c
index 52a5baa..9660286 100644
--- a/sys/arm/arm/trap.c
+++ b/sys/arm/arm/trap.c
@@ -365,19 +365,8 @@ abort_handler(struct trapframe *tf, int type)
 
 	onfault = pcb->pcb_onfault;
 	pcb->pcb_onfault = NULL;
-	if (map != kernel_map) {
-		PROC_LOCK(p);
-		p->p_lock++;
-		PROC_UNLOCK(p);
-	}
 	error = vm_fault(map, va, ftype, VM_FAULT_NORMAL);
 	pcb->pcb_onfault = onfault;
-
-	if (map != kernel_map) {
-		PROC_LOCK(p);
-		p->p_lock--;
-		PROC_UNLOCK(p);
-	}
 	if (__predict_true(error == 0))
 		goto out;
 fatal_pagefault:
@@ -682,20 +671,8 @@ prefetch_abort_handler(struct trapframe *tf)
 	if (pmap_fault_fixup(map->pmap, va, VM_PROT_READ, 1))
 		goto out;
 
-	if (map != kernel_map) {
-		PROC_LOCK(p);
-		p->p_lock++;
-		PROC_UNLOCK(p);
-	}
-
 	error = vm_fault(map, va, VM_PROT_READ | VM_PROT_EXECUTE,
 	    VM_FAULT_NORMAL);
-	if (map != kernel_map) {
-		PROC_LOCK(p);
-		p->p_lock--;
-		PROC_UNLOCK(p);
-	}
-
 	if (__predict_true(error == 0))
 		goto out;
 
diff --git a/sys/arm64/arm64/trap.c b/sys/arm64/arm64/trap.c
index 249322e..2a3cfb9 100644
--- a/sys/arm64/arm64/trap.c
+++ b/sys/arm64/arm64/trap.c
@@ -190,29 +190,8 @@ data_abort(struct trapframe *frame, uint64_t esr, int lower)
 	va = trunc_page(far);
 	ftype = ((esr >> 6) & 1) ? VM_PROT_READ | VM_PROT_WRITE : VM_PROT_READ;
 
-	if (map != kernel_map) {
-		/*
-		 * Keep swapout from messing with us during this
-		 *	critical time.
-		 */
-		PROC_LOCK(p);
-		++p->p_lock;
-		PROC_UNLOCK(p);
-
-		/* Fault in the user page: */
-		error = vm_fault(map, va, ftype, VM_FAULT_NORMAL);
-
-		PROC_LOCK(p);
-		--p->p_lock;
-		PROC_UNLOCK(p);
-	} else {
-		/*
-		 * Don't have to worry about process locking or stacks in the
-		 * kernel.
-		 */
-		error = vm_fault(map, va, ftype, VM_FAULT_NORMAL);
-	}
-
+	/* Fault in the page. */
+	error = vm_fault(map, va, ftype, VM_FAULT_NORMAL);
 	if (error != KERN_SUCCESS) {
 		if (lower) {
 			sig = SIGSEGV;
diff --git a/sys/i386/i386/trap.c b/sys/i386/i386/trap.c
index 1e417bf..a3b1b0d 100644
--- a/sys/i386/i386/trap.c
+++ b/sys/i386/i386/trap.c
@@ -782,7 +782,6 @@ trap_pfault(frame, usermode, eva)
 	vm_offset_t eva;
 {
 	vm_offset_t va;
-	struct vmspace *vm;
 	vm_map_t map;
 	int rv = 0;
 	vm_prot_t ftype;
@@ -852,14 +851,7 @@ trap_pfault(frame, usermode, eva)
 
 		map = kernel_map;
 	} else {
-		/*
-		 * This is a fault on non-kernel virtual memory.  If either
-		 * p or p->p_vmspace is NULL, then the fault is fatal.
-		 */
-		if (p == NULL || (vm = p->p_vmspace) == NULL)
-			goto nogo;
-
-		map = &vm->vm_map;
+		map = &p->p_vmspace->vm_map;
 
 		/*
 		 * When accessing a user-space address, kernel must be
@@ -888,28 +880,8 @@ trap_pfault(frame, usermode, eva)
 	else
 		ftype = VM_PROT_READ;
 
-	if (map != kernel_map) {
-		/*
-		 * Keep swapout from messing with us during this
-		 *	critical time.
-		 */
-		PROC_LOCK(p);
-		++p->p_lock;
-		PROC_UNLOCK(p);
-
-		/* Fault in the user page: */
-		rv = vm_fault(map, va, ftype, VM_FAULT_NORMAL);
-
-		PROC_LOCK(p);
-		--p->p_lock;
-		PROC_UNLOCK(p);
-	} else {
-		/*
-		 * Don't have to worry about process locking or stacks in the
-		 * kernel.
-		 */
-		rv = vm_fault(map, va, ftype, VM_FAULT_NORMAL);
-	}
+	/* Fault in the page. */
+	rv = vm_fault(map, va, ftype, VM_FAULT_NORMAL);
 	if (rv == KERN_SUCCESS) {
 #ifdef HWPMC_HOOKS
 		if (ftype == VM_PROT_READ || ftype == VM_PROT_WRITE) {
diff --git a/sys/mips/mips/trap.c b/sys/mips/mips/trap.c
index 98fe812..b193463 100644
--- a/sys/mips/mips/trap.c
+++ b/sys/mips/mips/trap.c
@@ -714,19 +714,7 @@ dofault:
 				goto nogo;
 			}
 
-			/*
-			 * Keep swapout from messing with us during this
-			 * critical time.
-			 */
-			PROC_LOCK(p);
-			++p->p_lock;
-			PROC_UNLOCK(p);
-
 			rv = vm_fault(map, va, ftype, VM_FAULT_NORMAL);
-
-			PROC_LOCK(p);
-			--p->p_lock;
-			PROC_UNLOCK(p);
 			/*
 			 * XXXDTRACE: add dtrace_doubletrap_func here?
 			 */
diff --git a/sys/powerpc/powerpc/trap.c b/sys/powerpc/powerpc/trap.c
index cabf780..29130ea 100644
--- a/sys/powerpc/powerpc/trap.c
+++ b/sys/powerpc/powerpc/trap.c
@@ -704,9 +704,6 @@ trap_pfault(struct trapframe *frame, int user)
 #else
 		if ((eva >> ADDR_SR_SHFT) == (USER_ADDR >> ADDR_SR_SHFT)) {
 #endif
-			if (p->p_vmspace == NULL)
-				return (SIGSEGV);
-
 			map = &p->p_vmspace->vm_map;
 
 #ifdef AIM
@@ -720,31 +717,11 @@ trap_pfault(struct trapframe *frame, int user)
 	}
 	va = trunc_page(eva);
 
-	if (map != kernel_map) {
-		/*
-		 * Keep swapout from messing with us during this
-		 *	critical time.
-		 */
-		PROC_LOCK(p);
-		++p->p_lock;
-		PROC_UNLOCK(p);
-
-		/* Fault in the user page: */
-		rv = vm_fault(map, va, ftype, VM_FAULT_NORMAL);
-
-		PROC_LOCK(p);
-		--p->p_lock;
-		PROC_UNLOCK(p);
-		/*
-		 * XXXDTRACE: add dtrace_doubletrap_func here?
-		 */
-	} else {
-		/*
-		 * Don't have to worry about process locking or stacks in the
-		 * kernel.
-		 */
-		rv = vm_fault(map, va, ftype, VM_FAULT_NORMAL);
-	}
+	/* Fault in the page. */
+	rv = vm_fault(map, va, ftype, VM_FAULT_NORMAL);
+	/*
+	 * XXXDTRACE: add dtrace_doubletrap_func here?
+	 */
 
 	if (rv == KERN_SUCCESS)
 		return (0);
diff --git a/sys/sparc64/sparc64/trap.c b/sys/sparc64/sparc64/trap.c
index e9917e5..96e72ed 100644
--- a/sys/sparc64/sparc64/trap.c
+++ b/sys/sparc64/sparc64/trap.c
@@ -441,7 +441,7 @@ trap_cecc(void)
 static int
 trap_pfault(struct thread *td, struct trapframe *tf)
 {
-	struct vmspace *vm;
+	vm_map_t map;
 	struct proc *p;
 	vm_offset_t va;
 	vm_prot_t prot;
@@ -484,28 +484,8 @@ trap_pfault(struct thread *td, struct trapframe *tf)
 			return (0);
 		}
 
-		/*
-		 * This is a fault on non-kernel virtual memory.
-		 */
-		vm = p->p_vmspace;
-
-		/*
-		 * Keep swapout from messing with us during this
-		 * critical time.
-		 */
-		PROC_LOCK(p);
-		++p->p_lock;
-		PROC_UNLOCK(p);
-
-		/* Fault in the user page. */
-		rv = vm_fault(&vm->vm_map, va, prot, VM_FAULT_NORMAL);
-
-		/*
-		 * Now the process can be swapped again.
-		 */
-		PROC_LOCK(p);
-		--p->p_lock;
-		PROC_UNLOCK(p);
+		/* This is a fault on non-kernel virtual memory. */
+		map = &p->p_vmspace->vm_map;
 	} else {
 		/*
 		 * This is a fault on kernel virtual memory.  Attempts to
@@ -527,14 +507,12 @@ trap_pfault(struct thread *td, struct trapframe *tf)
 			}
 			vm_map_unlock_read(kernel_map);
 		}
-
-		/*
-		 * We don't have to worry about process locking or stacks in
-		 * the kernel.
-		 */
-		rv = vm_fault(kernel_map, va, prot, VM_FAULT_NORMAL);
+		map = kernel_map;
 	}
 
+	/* Fault in the page. */
+	rv = vm_fault(map, va, prot, VM_FAULT_NORMAL);
+
 	CTR3(KTR_TRAP, "trap_pfault: return td=%p va=%#lx rv=%d",
 	    td, va, rv);
 	if (rv == KERN_SUCCESS)