[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.

include/linux/acct.h

@@ -121,12 +121,16 @@ struct vfsmount;
 struct super_block;
 extern void acct_auto_close_mnt(struct vfsmount *m);
 extern void acct_auto_close(struct super_block *sb);
+extern void acct_init_pacct(struct pacct_struct *pacct);
+extern void acct_collect();
 extern void acct_process(long exitcode);
 extern void acct_update_integrals(struct task_struct *tsk);
 extern void acct_clear_integrals(struct task_struct *tsk);
 #else
 #define acct_auto_close_mnt(x)	do { } while (0)
 #define acct_auto_close(x)	do { } while (0)
+#define acct_init_pacct(x)	do { } while (0)
+#define acct_collect()		do { } while (0)
 #define acct_process(x)		do { } while (0)
 #define acct_update_integrals(x)		do { } while (0)
 #define acct_clear_integrals(task)	do { } while (0)

include/linux/sched.h

@@ -358,6 +358,10 @@ struct sighand_struct {
 	spinlock_t		siglock;
 };
 
+struct pacct_struct {
+	unsigned long		ac_mem;
+};
+
 /*
  * NOTE! "signal_struct" does not have it's own
  * locking, because a shared signal_struct always
@@ -449,6 +453,9 @@ struct signal_struct {
 	struct key *session_keyring;	/* keyring inherited over fork */
 	struct key *process_keyring;	/* keyring private to this process */
 #endif
+#ifdef CONFIG_BSD_PROCESS_ACCT
+	struct pacct_struct pacct;	/* per-process accounting information */
+#endif
 };
 
 /* Context switch must be unlocked if interrupts are to be enabled */

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 +
@@ -545,6 +534,38 @@ static void do_acct_process(long exitcode, struct file *file)
 	set_fs(fs);
 }
 
+/**
+ * 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

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);

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;
 }