From: Anton Vorontsov <anton.vorontsov@linaro.org>
To: Andrew Morton <akpm@linux-foundation.org>,
Oleg Nesterov <oleg@redhat.com>
Cc: Russell King <linux@arm.linux.org.uk>,
Mike Frysinger <vapier@gentoo.org>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Richard Weinberger <richard@nod.at>,
Paul Mundt <lethal@linux-sh.org>,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
John Stultz <john.stultz@linaro.org>,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org,
uclinux-dist-devel@blackfin.uclinux.org,
linuxppc-dev@lists.ozlabs.org, linux-sh@vger.kernel.org,
user-mode-linux-devel@lists.sourceforge.net,
linaro-kernel@lists.linaro.org, patches@linaro.org,
linux-mm@kvack.org
Subject: [PATCH 5/9] blackfin: A couple of task->mm handling fixes
Date: Mon, 23 Apr 2012 00:09:01 -0700 [thread overview]
Message-ID: <20120423070901.GE30752@lizard> (raw)
In-Reply-To: <20120423070641.GA27702@lizard>
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>
---
arch/blackfin/kernel/trace.c | 26 +++++++++++++-------------
1 file changed, 13 insertions(+), 13 deletions(-)
diff --git a/arch/blackfin/kernel/trace.c b/arch/blackfin/kernel/trace.c
index 44bbf2f..d08f0e3 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);
}
/*
--
1.7.9.2
next prev parent reply other threads:[~2012-04-23 7:10 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-04-23 7:06 [PATCH v3 0/9] Fixes for common mistakes w/ for_each_process and task->mm Anton Vorontsov
2012-04-23 7:07 ` [PATCH 1/9] cpu: Introduce clear_tasks_mm_cpumask() helper Anton Vorontsov
2012-04-26 23:59 ` Andrew Morton
2012-05-01 10:45 ` Peter Zijlstra
2012-05-05 1:47 ` [PATCH] cpu: Document clear_tasks_mm_cpumask() Anton Vorontsov
2012-05-05 1:47 ` [PATCH 1/9] cpu: Introduce clear_tasks_mm_cpumask() helper Anton Vorontsov
2012-04-23 7:08 ` [PATCH 2/9] arm: Use clear_tasks_mm_cpumask() Anton Vorontsov
2012-04-23 7:08 ` [PATCH 3/9] powerpc: " Anton Vorontsov
2012-04-23 7:08 ` [PATCH 4/9] sh: " Anton Vorontsov
2012-04-23 7:09 ` Anton Vorontsov [this message]
2012-06-01 4:36 ` [PATCH 5/9] blackfin: A couple of task->mm handling fixes Mike Frysinger
2012-04-23 7:09 ` [PATCH 6/9] blackfin: Fix possible deadlock in decode_address() Anton Vorontsov
2012-04-23 7:09 ` [PATCH 7/9] um: Should hold tasklist_lock while traversing processes Anton Vorontsov
2012-04-23 14:57 ` Richard Weinberger
2012-04-23 15:40 ` Anton Vorontsov
2012-04-23 7:09 ` [PATCH 8/9] um: Fix possible race on task->mm Anton Vorontsov
2012-04-23 7:09 ` [PATCH 9/9] um: Properly check all process' threads for a live mm Anton Vorontsov
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