[PATCH] pacct: add pacct_struct to fix some pacct bugs.

The pacct facility need an i/o operation when an accounting record is
generated.  There is a possibility to wake OOM killer up.  If OOM killer is
activated, it kills some processes to make them release process memory
regions.

But acct_process() is called in the killed processes context before calling
exit_mm(), so those processes cannot release own memory.  In the results, any
processes stop in this point and it finally cause a system stall.

3 files changed, 40 insertions, 16 deletions

diff --git a/kernel/acct.c b/kernel/acct.c
index 44dd6bd..b352631 100644
--- a/kernel/acct.c
+++ b/kernel/acct.c
@@ -421,9 +421,9 @@ static u32 encode_float(u64 value)
  */
 static void do_acct_process(long exitcode, struct file *file)
 {
+	struct pacct_struct *pacct = &current->signal->pacct;
 	acct_t ac;
 	mm_segment_t fs;
-	unsigned long vsize;
 	unsigned long flim;
 	u64 elapsed;
 	u64 run_time;
@@ -505,20 +505,9 @@ static void do_acct_process(long exitcode, struct file *file)
 		ac.ac_flag |= ACORE;
 	if (current->flags & PF_SIGNALED)
 		ac.ac_flag |= AXSIG;
-
-	vsize = 0;
-	if (current->mm) {
-		struct vm_area_struct *vma;
-		down_read(&current->mm->mmap_sem);
-		vma = current->mm->mmap;
-		while (vma) {
-			vsize += vma->vm_end - vma->vm_start;
-			vma = vma->vm_next;
-		}
-		up_read(&current->mm->mmap_sem);
-	}
-	vsize = vsize / 1024;
-	ac.ac_mem = encode_comp_t(vsize);
+	spin_lock(&current->sighand->siglock);
+	ac.ac_mem = encode_comp_t(pacct->ac_mem);
+	spin_unlock(&current->sighand->siglock);
 	ac.ac_io = encode_comp_t(0 /* current->io_usage */);	/* %% */
 	ac.ac_rw = encode_comp_t(ac.ac_io / 1024);
 	ac.ac_minflt = encode_comp_t(current->signal->min_flt +
@@ -546,6 +535,38 @@ static void do_acct_process(long exitcode, struct file *file)
 }
 
 /**
+ * acct_init_pacct - initialize a new pacct_struct
+ */
+void acct_init_pacct(struct pacct_struct *pacct)
+{
+	memset(pacct, 0, sizeof(struct pacct_struct));
+}
+
+/**
+ * acct_collect - collect accounting information into pacct_struct
+ */
+void acct_collect(void)
+{
+	struct pacct_struct *pacct = &current->signal->pacct;
+	unsigned long vsize = 0;
+
+	if (current->mm) {
+		struct vm_area_struct *vma;
+		down_read(&current->mm->mmap_sem);
+		vma = current->mm->mmap;
+		while (vma) {
+			vsize += vma->vm_end - vma->vm_start;
+			vma = vma->vm_next;
+		}
+		up_read(&current->mm->mmap_sem);
+	}
+
+	spin_lock(&current->sighand->siglock);
+	pacct->ac_mem = vsize / 1024;
+	spin_unlock(&current->sighand->siglock);
+}
+
+/**
  * acct_process - now just a wrapper around do_acct_process
  * @exitcode: task exit code
  *
diff --git a/kernel/exit.c b/kernel/exit.c
index 601263c..819d82c 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -894,7 +894,7 @@ fastcall NORET_TYPE void do_exit(long code)
 	if (group_dead) {
  		hrtimer_cancel(&tsk->signal->real_timer);
 		exit_itimers(tsk->signal);
-		acct_process(code);
+		acct_collect();
 	}
 	if (unlikely(tsk->robust_list))
 		exit_robust_list(tsk);
@@ -906,6 +906,8 @@ fastcall NORET_TYPE void do_exit(long code)
 		audit_free(tsk);
 	exit_mm(tsk);
 
+	if (group_dead)
+		acct_process(code);
 	exit_sem(tsk);
 	__exit_files(tsk);
 	__exit_fs(tsk);
diff --git a/kernel/fork.c b/kernel/fork.c
index 49adc0e..dfd10cb 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -874,6 +874,7 @@ static inline int copy_signal(unsigned long clone_flags, struct task_struct * ts
 		tsk->it_prof_expires =
 			secs_to_cputime(sig->rlim[RLIMIT_CPU].rlim_cur);
 	}
+	acct_init_pacct(&sig->pacct);
 
 	return 0;
 }