diff options
| author | Anton Vorontsov <anton.vorontsov@linaro.org> | 2012-05-31 16:26:24 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2012-05-31 17:49:30 -0700 |
| commit | 2214f707de257c35773d5cd68cec9e31b91e01ca (patch) | |
| tree | c25a6a2b3f83704fbf03efa6d6c5f8e6ee15c856 | |
| parent | 1198c8b9af611bb697d92259095d7cc20f5c961d (diff) | |
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>
| -rw-r--r-- | arch/blackfin/kernel/trace.c | 26 |
1 files changed, 13 insertions, 13 deletions
diff --git a/arch/blackfin/kernel/trace.c b/arch/blackfin/kernel/trace.c index 44bbf2f564cb..d08f0e3e2dcc 100644 --- a/arch/blackfin/kernel/trace.c +++ b/arch/blackfin/kernel/trace.c @@ -10,6 +10,8 @@ #include <linux/hardirq.h> #include <linux/thread_info.h> #include <linux/mm.h> +#include <linux/oom.h> +#include <linux/sched.h> #include <linux/uaccess.h> #include <linux/module.h> #include <linux/kallsyms.h> @@ -28,7 +30,6 @@ void decode_address(char *buf, unsigned long address) struct task_struct *p; struct mm_struct *mm; unsigned long flags, offset; - unsigned char in_atomic = (bfin_read_IPEND() & 0x10) || in_atomic(); struct rb_node *n; #ifdef CONFIG_KALLSYMS @@ -114,15 +115,15 @@ void decode_address(char *buf, unsigned long address) */ write_lock_irqsave(&tasklist_lock, flags); for_each_process(p) { - mm = (in_atomic ? p->mm : get_task_mm(p)); - if (!mm) - continue; + struct task_struct *t; - if (!down_read_trylock(&mm->mmap_sem)) { - if (!in_atomic) - mmput(mm); + t = find_lock_task_mm(p); + if (!t) continue; - } + + mm = t->mm; + if (!down_read_trylock(&mm->mmap_sem)) + goto __continue; for (n = rb_first(&mm->mm_rb); n; n = rb_next(n)) { struct vm_area_struct *vma; @@ -131,7 +132,7 @@ void decode_address(char *buf, unsigned long address) if (address >= vma->vm_start && address < vma->vm_end) { char _tmpbuf[256]; - char *name = p->comm; + char *name = t->comm; struct file *file = vma->vm_file; if (file) { @@ -164,8 +165,7 @@ void decode_address(char *buf, unsigned long address) name, vma->vm_start, vma->vm_end); up_read(&mm->mmap_sem); - if (!in_atomic) - mmput(mm); + task_unlock(t); if (buf[0] == '\0') sprintf(buf, "[ %s ] dynamic memory", name); @@ -175,8 +175,8 @@ void decode_address(char *buf, unsigned long address) } up_read(&mm->mmap_sem); - if (!in_atomic) - mmput(mm); +__continue: + task_unlock(t); } /* |