[PATCH] mm, arch: Complete pagefault_disable abstraction

[PATCH] mm, arch: Complete pagefault_disable abstraction

[Peter Zijlstra]

Subject: mm, arch: Complete pagefault_disable abstraction
From: Peter Zijlstra <a.p.zijlstra@chello.nl>
Date: Wed Oct 05 14:22:37 CEST 2011

Currently we already have pagefault_{disable,enable}() but they're
nothing more than a glorified preempt_{disable,enable}().

For -rt we want to make pagefault_disable() regions preemptible and
for that we need to complete the abstraction, replace the current
in_atomic() tests that are relevant to pagefault_disable() usage with
pagefault_disabled().

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
---
 arch/alpha/mm/fault.c      |    2 +-
 arch/arm/mm/fault.c        |    2 +-
 arch/avr32/mm/fault.c      |    2 +-
 arch/cris/mm/fault.c       |    2 +-
 arch/frv/mm/fault.c        |    2 +-
 arch/ia64/mm/fault.c       |    2 +-
 arch/m32r/mm/fault.c       |    2 +-
 arch/m68k/mm/fault.c       |    2 +-
 arch/microblaze/mm/fault.c |    2 +-
 arch/mips/mm/fault.c       |    2 +-
 arch/mn10300/mm/fault.c    |    2 +-
 arch/parisc/mm/fault.c     |    2 +-
 arch/powerpc/mm/fault.c    |    2 +-
 arch/s390/mm/fault.c       |    6 ++++--
 arch/score/mm/fault.c      |    2 +-
 arch/sh/mm/fault_32.c      |    2 +-
 arch/sparc/mm/fault_32.c   |    4 ++--
 arch/sparc/mm/fault_64.c   |    2 +-
 arch/tile/mm/fault.c       |    2 +-
 arch/um/kernel/trap.c      |    2 +-
 arch/unicore32/mm/fault.c  |    2 +-
 arch/x86/mm/fault.c        |    2 +-
 arch/xtensa/mm/fault.c     |    2 +-
 include/linux/sched.h      |    6 ++++++
 mm/filemap.c               |    2 +-
 25 files changed, 34 insertions(+), 26 deletions(-)

Index: linux-2.6/arch/alpha/mm/fault.c
===================================================================
--- linux-2.6.orig/arch/alpha/mm/fault.c
+++ linux-2.6/arch/alpha/mm/fault.c
@@ -107,7 +107,7 @@ do_page_fault(unsigned long address, uns
 
 	/* If we're in an interrupt context, or have no user context,
 	   we must not take the fault.  */
-	if (!mm || in_atomic())
+	if (!mm || pagefault_disabled())
 		goto no_context;
 
 #ifdef CONFIG_ALPHA_LARGE_VMALLOC
Index: linux-2.6/arch/arm/mm/fault.c
===================================================================
--- linux-2.6.orig/arch/arm/mm/fault.c
+++ linux-2.6/arch/arm/mm/fault.c
@@ -293,7 +293,7 @@ do_page_fault(unsigned long addr, unsign
 	 * If we're in an interrupt or have no user
 	 * context, we must not take the fault..
 	 */
-	if (in_atomic() || !mm)
+	if (!mm || pagefault_disabled())
 		goto no_context;
 
 	/*
Index: linux-2.6/arch/avr32/mm/fault.c
===================================================================
--- linux-2.6.orig/arch/avr32/mm/fault.c
+++ linux-2.6/arch/avr32/mm/fault.c
@@ -81,7 +81,7 @@ asmlinkage void do_page_fault(unsigned l
 	 * If we're in an interrupt or have no user context, we must
 	 * not take the fault...
 	 */
-	if (in_atomic() || !mm || regs->sr & SYSREG_BIT(GM))
+	if (!mm || regs->sr & SYSREG_BIT(GM) || pagefault_disabled())
 		goto no_context;
 
 	local_irq_enable();
Index: linux-2.6/arch/cris/mm/fault.c
===================================================================
--- linux-2.6.orig/arch/cris/mm/fault.c
+++ linux-2.6/arch/cris/mm/fault.c
@@ -111,7 +111,7 @@ do_page_fault(unsigned long address, str
 	 * user context, we must not take the fault.
 	 */
 
-	if (in_atomic() || !mm)
+	if (!mm || pagefault_disabled())
 		goto no_context;
 
 	down_read(&mm->mmap_sem);
Index: linux-2.6/arch/frv/mm/fault.c
===================================================================
--- linux-2.6.orig/arch/frv/mm/fault.c
+++ linux-2.6/arch/frv/mm/fault.c
@@ -79,7 +79,7 @@ asmlinkage void do_page_fault(int datamm
 	 * If we're in an interrupt or have no user
 	 * context, we must not take the fault..
 	 */
-	if (in_atomic() || !mm)
+	if (!mm || pagefault_disabled())
 		goto no_context;
 
 	down_read(&mm->mmap_sem);
Index: linux-2.6/arch/ia64/mm/fault.c
===================================================================
--- linux-2.6.orig/arch/ia64/mm/fault.c
+++ linux-2.6/arch/ia64/mm/fault.c
@@ -89,7 +89,7 @@ ia64_do_page_fault (unsigned long addres
 	/*
 	 * If we're in an interrupt or have no user context, we must not take the fault..
 	 */
-	if (in_atomic() || !mm)
+	if (!mm || pagefault_disabled())
 		goto no_context;
 
 #ifdef CONFIG_VIRTUAL_MEM_MAP
Index: linux-2.6/arch/m32r/mm/fault.c
===================================================================
--- linux-2.6.orig/arch/m32r/mm/fault.c
+++ linux-2.6/arch/m32r/mm/fault.c
@@ -115,7 +115,7 @@ asmlinkage void do_page_fault(struct pt_
 	 * If we're in an interrupt or have no user context or are running in an
 	 * atomic region then we must not take the fault..
 	 */
-	if (in_atomic() || !mm)
+	if (!mm || pagefault_disabled())
 		goto bad_area_nosemaphore;
 
 	/* When running in the kernel we expect faults to occur only to
Index: linux-2.6/arch/m68k/mm/fault.c
===================================================================
--- linux-2.6.orig/arch/m68k/mm/fault.c
+++ linux-2.6/arch/m68k/mm/fault.c
@@ -85,7 +85,7 @@ int do_page_fault(struct pt_regs *regs,
 	 * If we're in an interrupt or have no user
 	 * context, we must not take the fault..
 	 */
-	if (in_atomic() || !mm)
+	if (!mm || pagefault_disabled())
 		goto no_context;
 
 	down_read(&mm->mmap_sem);
Index: linux-2.6/arch/microblaze/mm/fault.c
===================================================================
--- linux-2.6.orig/arch/microblaze/mm/fault.c
+++ linux-2.6/arch/microblaze/mm/fault.c
@@ -107,7 +107,7 @@ void do_page_fault(struct pt_regs *regs,
 	if ((error_code & 0x13) == 0x13 || (error_code & 0x11) == 0x11)
 		is_write = 0;
 
-	if (unlikely(in_atomic() || !mm)) {
+	if (unlikely(!mm || pagefault_disabled())) {
 		if (kernel_mode(regs))
 			goto bad_area_nosemaphore;
 
Index: linux-2.6/arch/mips/mm/fault.c
===================================================================
--- linux-2.6.orig/arch/mips/mm/fault.c
+++ linux-2.6/arch/mips/mm/fault.c
@@ -88,7 +88,7 @@ asmlinkage void __kprobes do_page_fault(
 	 * If we're in an interrupt or have no user
 	 * context, we must not take the fault..
 	 */
-	if (in_atomic() || !mm)
+	if (!mm || pagefault_disabled())
 		goto bad_area_nosemaphore;
 
 	down_read(&mm->mmap_sem);
Index: linux-2.6/arch/mn10300/mm/fault.c
===================================================================
--- linux-2.6.orig/arch/mn10300/mm/fault.c
+++ linux-2.6/arch/mn10300/mm/fault.c
@@ -168,7 +168,7 @@ asmlinkage void do_page_fault(struct pt_
 	 * If we're in an interrupt or have no user
 	 * context, we must not take the fault..
 	 */
-	if (in_atomic() || !mm)
+	if (!mm || pagefault_disabled())
 		goto no_context;
 
 	down_read(&mm->mmap_sem);
Index: linux-2.6/arch/parisc/mm/fault.c
===================================================================
--- linux-2.6.orig/arch/parisc/mm/fault.c
+++ linux-2.6/arch/parisc/mm/fault.c
@@ -176,7 +176,7 @@ void do_page_fault(struct pt_regs *regs,
 	unsigned long acc_type;
 	int fault;
 
-	if (in_atomic() || !mm)
+	if (!mm || pagefault_disabled())
 		goto no_context;
 
 	down_read(&mm->mmap_sem);
Index: linux-2.6/arch/powerpc/mm/fault.c
===================================================================
--- linux-2.6.orig/arch/powerpc/mm/fault.c
+++ linux-2.6/arch/powerpc/mm/fault.c
@@ -162,7 +162,7 @@ int __kprobes do_page_fault(struct pt_re
 	}
 #endif
 
-	if (in_atomic() || mm == NULL) {
+	if (!mm || pagefault_disabled()) {
 		if (!user_mode(regs))
 			return SIGSEGV;
 		/* in_atomic() in user mode is really bad,
Index: linux-2.6/arch/s390/mm/fault.c
===================================================================
--- linux-2.6.orig/arch/s390/mm/fault.c
+++ linux-2.6/arch/s390/mm/fault.c
@@ -295,7 +295,8 @@ static inline int do_exception(struct pt
 	 * user context.
 	 */
 	fault = VM_FAULT_BADCONTEXT;
-	if (unlikely(!user_space_fault(trans_exc_code) || in_atomic() || !mm))
+	if (unlikely(!user_space_fault(trans_exc_code) ||
+		     !mm || pagefault_disabled()))
 		goto out;
 
 	address = trans_exc_code & __FAIL_ADDR_MASK;
@@ -426,7 +427,8 @@ void __kprobes do_asce_exception(struct
 	struct mm_struct *mm = current->mm;
 	struct vm_area_struct *vma;
 
-	if (unlikely(!user_space_fault(trans_exc_code) || in_atomic() || !mm))
+	if (unlikely(!user_space_fault(trans_exc_code) ||
+		     !mm || pagefault_disabled()))
 		goto no_context;
 
 	down_read(&mm->mmap_sem);
Index: linux-2.6/arch/score/mm/fault.c
===================================================================
--- linux-2.6.orig/arch/score/mm/fault.c
+++ linux-2.6/arch/score/mm/fault.c
@@ -72,7 +72,7 @@ asmlinkage void do_page_fault(struct pt_
 	* If we're in an interrupt or have no user
 	* context, we must not take the fault..
 	*/
-	if (in_atomic() || !mm)
+	if (!mm || pagefault_disabled())
 		goto bad_area_nosemaphore;
 
 	down_read(&mm->mmap_sem);
Index: linux-2.6/arch/sh/mm/fault_32.c
===================================================================
--- linux-2.6.orig/arch/sh/mm/fault_32.c
+++ linux-2.6/arch/sh/mm/fault_32.c
@@ -166,7 +166,7 @@ asmlinkage void __kprobes do_page_fault(
 	 * If we're in an interrupt, have no user context or are running
 	 * in an atomic region then we must not take the fault:
 	 */
-	if (in_atomic() || !mm)
+	if (!mm || pagefault_disabled())
 		goto no_context;
 
 	down_read(&mm->mmap_sem);
Index: linux-2.6/arch/sparc/mm/fault_32.c
===================================================================
--- linux-2.6.orig/arch/sparc/mm/fault_32.c
+++ linux-2.6/arch/sparc/mm/fault_32.c
@@ -248,8 +248,8 @@ asmlinkage void do_sparc_fault(struct pt
 	 * If we're in an interrupt or have no user
 	 * context, we must not take the fault..
 	 */
-        if (in_atomic() || !mm)
-                goto no_context;
+	if (!mm || pagefault_disabled())
+		goto no_context;
 
 	perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
 
Index: linux-2.6/arch/sparc/mm/fault_64.c
===================================================================
--- linux-2.6.orig/arch/sparc/mm/fault_64.c
+++ linux-2.6/arch/sparc/mm/fault_64.c
@@ -322,7 +322,7 @@ asmlinkage void __kprobes do_sparc64_fau
 	 * If we're in an interrupt or have no user
 	 * context, we must not take the fault..
 	 */
-	if (in_atomic() || !mm)
+	if (!mm || pagefault_disabled())
 		goto intr_or_no_mm;
 
 	perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
Index: linux-2.6/arch/tile/mm/fault.c
===================================================================
--- linux-2.6.orig/arch/tile/mm/fault.c
+++ linux-2.6/arch/tile/mm/fault.c
@@ -346,7 +346,7 @@ static int handle_page_fault(struct pt_r
 	 * If we're in an interrupt, have no user context or are running in an
 	 * atomic region then we must not take the fault.
 	 */
-	if (in_atomic() || !mm) {
+	if (!mm || pagefault_disabled()) {
 		vma = NULL;  /* happy compiler */
 		goto bad_area_nosemaphore;
 	}
Index: linux-2.6/arch/um/kernel/trap.c
===================================================================
--- linux-2.6.orig/arch/um/kernel/trap.c
+++ linux-2.6/arch/um/kernel/trap.c
@@ -37,7 +37,7 @@ int handle_page_fault(unsigned long addr
 	 * If the fault was during atomic operation, don't take the fault, just
 	 * fail.
 	 */
-	if (in_atomic())
+	if (!mm || pagefault_disabled())
 		goto out_nosemaphore;
 
 	down_read(&mm->mmap_sem);
Index: linux-2.6/arch/unicore32/mm/fault.c
===================================================================
--- linux-2.6.orig/arch/unicore32/mm/fault.c
+++ linux-2.6/arch/unicore32/mm/fault.c
@@ -225,7 +225,7 @@ static int do_pf(unsigned long addr, uns
 	 * If we're in an interrupt or have no user
 	 * context, we must not take the fault..
 	 */
-	if (in_atomic() || !mm)
+	if (!mm || pagefault_disabled())
 		goto no_context;
 
 	/*
Index: linux-2.6/arch/x86/mm/fault.c
===================================================================
--- linux-2.6.orig/arch/x86/mm/fault.c
+++ linux-2.6/arch/x86/mm/fault.c
@@ -1084,7 +1084,7 @@ do_page_fault(struct pt_regs *regs, unsi
 	 * If we're in an interrupt, have no user context or are running
 	 * in an atomic region then we must not take the fault:
 	 */
-	if (unlikely(in_atomic() || !mm)) {
+	if (unlikely(!mm || pagefault_disabled())) {
 		bad_area_nosemaphore(regs, error_code, address);
 		return;
 	}
Index: linux-2.6/arch/xtensa/mm/fault.c
===================================================================
--- linux-2.6.orig/arch/xtensa/mm/fault.c
+++ linux-2.6/arch/xtensa/mm/fault.c
@@ -57,7 +57,7 @@ void do_page_fault(struct pt_regs *regs)
 	/* If we're in an interrupt or have no user
 	 * context, we must not take the fault..
 	 */
-	if (in_atomic() || !mm) {
+	if (!mm || pagefault_disabled()) {
 		bad_page_fault(regs, address, SIGSEGV);
 		return;
 	}
Index: linux-2.6/include/linux/sched.h
===================================================================
--- linux-2.6.orig/include/linux/sched.h
+++ linux-2.6/include/linux/sched.h
@@ -91,6 +91,7 @@ struct sched_param {
 #include <linux/latencytop.h>
 #include <linux/cred.h>
 #include <linux/llist.h>
+#include <linux/hardirq.h>
 
 #include <asm/processor.h>
 
@@ -1575,6 +1576,11 @@ struct task_struct {
 /* Future-safe accessor for struct task_struct's cpus_allowed. */
 #define tsk_cpus_allowed(tsk) (&(tsk)->cpus_allowed)
 
+static inline bool pagefault_disabled(void)
+{
+	return in_atomic();
+}
+
 /*
  * Priority of a process goes from 0..MAX_PRIO-1, valid RT
  * priority is 0..MAX_RT_PRIO-1, and SCHED_NORMAL/SCHED_BATCH
Index: linux-2.6/mm/filemap.c
===================================================================
--- linux-2.6.orig/mm/filemap.c
+++ linux-2.6/mm/filemap.c
@@ -2061,7 +2061,7 @@ size_t iov_iter_copy_from_user_atomic(st
 	char *kaddr;
 	size_t copied;
 
-	BUG_ON(!in_atomic());
+	BUG_ON(!pagefault_disabled());
 	kaddr = kmap_atomic(page, KM_USER0);
 	if (likely(i->nr_segs == 1)) {
 		int left;

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>

Re: [PATCH] mm, arch: Complete pagefault_disable abstraction

[Peter Zijlstra]

For reference, here's the -rt patch that goes on top:

---
Subject: rt: Preemptable pagefault_disable()
From: Peter Zijlstra <a.p.zijlstra@chello.nl>
Date: Wed Oct 05 14:20:57 CEST 2011

Implement a preemptable pagefault_disable() by keeping a per-task
pagefault_disabled counter.

This allows disabling of the pagefault handler (and thus avoiding the
recursive fault/mmap_sem issues) without disabling preemption.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
---
 include/linux/sched.h   |    9 ++++++++-
 include/linux/uaccess.h |    5 +++++
 kernel/fork.c           |    3 +++
 mm/memory.c             |   24 ++++++++++++++++++++++++
 4 files changed, 40 insertions(+), 1 deletion(-)

Index: linux-2.6/include/linux/uaccess.h
===================================================================
--- linux-2.6.orig/include/linux/uaccess.h
+++ linux-2.6/include/linux/uaccess.h
@@ -4,6 +4,7 @@
 #include <linux/preempt.h>
 #include <asm/uaccess.h>
 
+#ifndef CONFIG_PREEMPT_RT_FULL
 /*
  * These routines enable/disable the pagefault handler in that
  * it will not take any locks and go straight to the fixup table.
@@ -37,6 +38,10 @@ static inline void pagefault_enable(void
 	barrier();
 	preempt_check_resched();
 }
+#else
+extern void pagefault_disable(void);
+extern void pagefault_enable(void);
+#endif
 
 #ifndef ARCH_HAS_NOCACHE_UACCESS
 
Index: linux-2.6/kernel/fork.c
===================================================================
--- linux-2.6.orig/kernel/fork.c
+++ linux-2.6/kernel/fork.c
@@ -1200,6 +1200,9 @@ static struct task_struct *copy_process(
 	p->hardirq_context = 0;
 	p->softirq_context = 0;
 #endif
+#ifdef CONFIG_PREEMPT_RT_FULL
+	p->pagefault_disabled = 0;
+#endif
 #ifdef CONFIG_LOCKDEP
 	p->lockdep_depth = 0; /* no locks held yet */
 	p->curr_chain_key = 0;
Index: linux-2.6/mm/memory.c
===================================================================
--- linux-2.6.orig/mm/memory.c
+++ linux-2.6/mm/memory.c
@@ -3436,6 +3436,30 @@ int handle_pte_fault(struct mm_struct *m
 	return 0;
 }
 
+#ifdef CONFIG_PREEMPT_RT_FULL
+void pagefault_disable(void)
+{
+	current->pagefault_disabled++;
+	/*
+	 * make sure to have issued the store before a pagefault
+	 * can hit.
+	 */
+	barrier();
+}
+EXPORT_SYMBOL_GPL(pagefault_disable);
+
+void pagefault_enable(void)
+{
+	/*
+	 * make sure to issue those last loads/stores before enabling
+	 * the pagefault handler again.
+	 */
+	barrier();
+	current->pagefault_disabled--;
+}
+EXPORT_SYMBOL_GPL(pagefault_enable);
+#endif
+
 /*
  * By the time we get here, we already hold the mm semaphore
  */
Index: linux-2.6/include/linux/sched.h
===================================================================
--- linux-2.6.orig/include/linux/sched.h
+++ linux-2.6/include/linux/sched.h
@@ -1434,6 +1434,9 @@ struct task_struct {
 	/* mutex deadlock detection */
 	struct mutex_waiter *blocked_on;
 #endif
+#ifdef CONFIG_PREEMPT_RT_FULL
+	int pagefault_disabled;
+#endif
 #ifdef CONFIG_TRACE_IRQFLAGS
 	unsigned int irq_events;
 	unsigned long hardirq_enable_ip;
@@ -1578,7 +1581,11 @@ struct task_struct {
 
 static inline bool pagefault_disabled(void)
 {
-	return in_atomic();
+	return in_atomic()
+#ifdef CONFIG_PREEMPT_RT_FULL
+		|| current->pagefault_disabled
+#endif
+		;
 }
 
 /*

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>

Re: [PATCH] mm, arch: Complete pagefault_disable abstraction

[Peter Zijlstra]

For those with a strong stomach, here's what we do with kmap_atomic:

---
Subject: mm, rt: kmap_atomic scheduling
From: Peter Zijlstra <peterz@infradead.org>
Date: Thu, 28 Jul 2011 10:43:51 +0200

In fact, with migrate_disable() existing one could play games with
kmap_atomic. You could save/restore the kmap_atomic slots on context
switch (if there are any in use of course), this should be esp easy now
that we have a kmap_atomic stack.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
[dvhart@linux.intel.com: build fix]
Link: http://lkml.kernel.org/r/1311842631.5890.208.camel@twins
---
 arch/x86/kernel/process_32.c |   36 ++++++++++++++++++++++++++++++++++++
 include/linux/sched.h        |    5 +++++
 mm/memory.c                  |    2 ++
 3 files changed, 43 insertions(+)

Index: linux-2.6/arch/x86/kernel/process_32.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/process_32.c
+++ linux-2.6/arch/x86/kernel/process_32.c
@@ -38,6 +38,7 @@
 #include <linux/uaccess.h>
 #include <linux/io.h>
 #include <linux/kdebug.h>
+#include <linux/highmem.h>
 
 #include <asm/pgtable.h>
 #include <asm/system.h>
@@ -346,6 +347,41 @@ __switch_to(struct task_struct *prev_p, 
 		     task_thread_info(next_p)->flags & _TIF_WORK_CTXSW_NEXT))
 		__switch_to_xtra(prev_p, next_p, tss);
 
+#if defined CONFIG_PREEMPT_RT_FULL && defined CONFIG_HIGHMEM
+	/*
+	 * Save @prev's kmap_atomic stack
+	 */
+	prev_p->kmap_idx = __this_cpu_read(__kmap_atomic_idx);
+	if (unlikely(prev_p->kmap_idx)) {
+		int i;
+
+		for (i = 0; i < prev_p->kmap_idx; i++) {
+			int idx = i + KM_TYPE_NR * smp_processor_id();
+
+			pte_t *ptep = kmap_pte - idx;
+			prev_p->kmap_pte[i] = *ptep;
+			kpte_clear_flush(ptep, __fix_to_virt(FIX_KMAP_BEGIN + idx));
+		}
+
+		__this_cpu_write(__kmap_atomic_idx, 0);
+	}
+
+	/*
+	 * Restore @next_p's kmap_atomic stack
+	 */
+	if (unlikely(next_p->kmap_idx)) {
+		int i;
+
+		__this_cpu_write(__kmap_atomic_idx, next_p->kmap_idx);
+
+		for (i = 0; i < next_p->kmap_idx; i++) {
+			int idx = i + KM_TYPE_NR * smp_processor_id();
+
+			set_pte(kmap_pte - idx, next_p->kmap_pte[i]);
+		}
+	}
+#endif
+
 	/* If we're going to preload the fpu context, make sure clts
 	   is run while we're batching the cpu state updates. */
 	if (preload_fpu)
Index: linux-2.6/include/linux/sched.h
===================================================================
--- linux-2.6.orig/include/linux/sched.h
+++ linux-2.6/include/linux/sched.h
@@ -63,6 +63,7 @@ struct sched_param {
 #include <linux/nodemask.h>
 #include <linux/mm_types.h>
 
+#include <asm/kmap_types.h>
 #include <asm/system.h>
 #include <asm/page.h>
 #include <asm/ptrace.h>
@@ -1594,6 +1595,10 @@ struct task_struct {
 	struct rcu_head put_rcu;
 	int softirq_nestcnt;
 #endif
+#if defined CONFIG_PREEMPT_RT_FULL && defined CONFIG_HIGHMEM
+	int kmap_idx;
+	pte_t kmap_pte[KM_TYPE_NR];
+#endif
 };
 
 #ifdef CONFIG_PREEMPT_RT_FULL
Index: linux-2.6/mm/memory.c
===================================================================
--- linux-2.6.orig/mm/memory.c
+++ linux-2.6/mm/memory.c
@@ -3431,6 +3431,7 @@ unlock:
 #ifdef CONFIG_PREEMPT_RT_FULL
 void pagefault_disable(void)
 {
+	migrate_disable();
 	current->pagefault_disabled++;
 	/*
 	 * make sure to have issued the store before a pagefault
@@ -3448,6 +3449,7 @@ void pagefault_enable(void)
 	 */
 	barrier();
 	current->pagefault_disabled--;
+	migrate_enable();
 }
 EXPORT_SYMBOL_GPL(pagefault_enable);
 #endif

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>

Re: [PATCH] mm, arch: Complete pagefault_disable abstraction

[Andrew Morton]

On Wed, 05 Oct 2011 15:09:29 +0200
Peter Zijlstra <peterz@infradead.org> wrote:

> Currently we already have pagefault_{disable,enable}() but they're
> nothing more than a glorified preempt_{disable,enable}().

That's not very accurate or useful.  Unlike preempt_disable(),
pagefault_disable() will raise the preempt count when CONFIG_PREEMPT=n.

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>