blackfin: a couple of task->mm handling fixes
The patch fixes two problems: 1. Working with task->mm w/o getting mm or grabing the task lock is dangerous as ->mm might disappear (exit_mm() assigns NULL under task_lock(), so tasklist lock is not enough). We can't use get_task_mm()/mmput() pair as mmput() might sleep, so we have to take the task lock while handle its mm. 2. Checking for process->mm is not enough because process' main thread may exit or detach its mm via use_mm(), but other threads may still have a valid mm. To catch this we use find_lock_task_mm(), which walks up all threads and returns an appropriate task (with task lock held). Suggested-by: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org> Cc: Mike Frysinger <vapier@gentoo.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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@ -10,6 +10,8 @@
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#include <linux/hardirq.h>
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#include <linux/hardirq.h>
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#include <linux/thread_info.h>
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#include <linux/thread_info.h>
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#include <linux/mm.h>
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#include <linux/mm.h>
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#include <linux/oom.h>
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#include <linux/sched.h>
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#include <linux/uaccess.h>
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#include <linux/uaccess.h>
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#include <linux/module.h>
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#include <linux/module.h>
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#include <linux/kallsyms.h>
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#include <linux/kallsyms.h>
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@ -28,7 +30,6 @@ void decode_address(char *buf, unsigned long address)
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struct task_struct *p;
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struct task_struct *p;
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struct mm_struct *mm;
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struct mm_struct *mm;
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unsigned long flags, offset;
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unsigned long flags, offset;
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unsigned char in_atomic = (bfin_read_IPEND() & 0x10) || in_atomic();
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struct rb_node *n;
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struct rb_node *n;
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#ifdef CONFIG_KALLSYMS
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#ifdef CONFIG_KALLSYMS
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@ -114,15 +115,15 @@ void decode_address(char *buf, unsigned long address)
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*/
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*/
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write_lock_irqsave(&tasklist_lock, flags);
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write_lock_irqsave(&tasklist_lock, flags);
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for_each_process(p) {
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for_each_process(p) {
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mm = (in_atomic ? p->mm : get_task_mm(p));
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struct task_struct *t;
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if (!mm)
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t = find_lock_task_mm(p);
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if (!t)
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continue;
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continue;
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if (!down_read_trylock(&mm->mmap_sem)) {
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mm = t->mm;
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if (!in_atomic)
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if (!down_read_trylock(&mm->mmap_sem))
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mmput(mm);
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goto __continue;
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continue;
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}
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for (n = rb_first(&mm->mm_rb); n; n = rb_next(n)) {
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for (n = rb_first(&mm->mm_rb); n; n = rb_next(n)) {
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struct vm_area_struct *vma;
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struct vm_area_struct *vma;
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@ -131,7 +132,7 @@ void decode_address(char *buf, unsigned long address)
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if (address >= vma->vm_start && address < vma->vm_end) {
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if (address >= vma->vm_start && address < vma->vm_end) {
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char _tmpbuf[256];
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char _tmpbuf[256];
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char *name = p->comm;
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char *name = t->comm;
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struct file *file = vma->vm_file;
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struct file *file = vma->vm_file;
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if (file) {
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if (file) {
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@ -164,8 +165,7 @@ void decode_address(char *buf, unsigned long address)
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name, vma->vm_start, vma->vm_end);
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name, vma->vm_start, vma->vm_end);
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up_read(&mm->mmap_sem);
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up_read(&mm->mmap_sem);
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if (!in_atomic)
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task_unlock(t);
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mmput(mm);
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if (buf[0] == '\0')
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if (buf[0] == '\0')
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sprintf(buf, "[ %s ] dynamic memory", name);
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sprintf(buf, "[ %s ] dynamic memory", name);
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@ -175,8 +175,8 @@ void decode_address(char *buf, unsigned long address)
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}
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}
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up_read(&mm->mmap_sem);
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up_read(&mm->mmap_sem);
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if (!in_atomic)
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__continue:
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mmput(mm);
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task_unlock(t);
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}
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}
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/*
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/*
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