[PATCH] pacct: none-delayed process accounting accumulation

In current 2.6.17 implementation, signal_struct refered from task_struct is
used for per-process data structure.  The pacct facility also uses it as a
per-process data structure to store stime, utime, minflt, majflt.  But those
members are saved in __exit_signal().  It's too late.

For example, if some threads exits at same time, pacct facility has a
possibility to drop accountings for a part of those threads.  (see, the
following 'The results of original 2.6.17 kernel') I think accounting
information should be completely collected into the per-process data structure
before writing out an accounting record.

This patch fixes this matter.  Accumulation of stime, utime, minflt and majflt
are done before generating accounting record.

[mingo@elte.hu: fix acct_collect() siglock bug found by lockdep]
Signed-off-by: KaiGai Kohei <kaigai@ak.jp.nec.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

include/linux/sched.h

@@ -362,6 +362,8 @@ struct pacct_struct {
 	int			ac_flag;
 	long			ac_exitcode;
 	unsigned long		ac_mem;
+	cputime_t		ac_utime, ac_stime;
+	unsigned long		ac_minflt, ac_majflt;
 };
 
 /*

kernel/acct.c

@@ -428,7 +428,6 @@ static void do_acct_process(struct file *file)
 	u64 elapsed;
 	u64 run_time;
 	struct timespec uptime;
-	unsigned long jiffies;
 
 	/*
 	 * First check to see if there is enough free_space to continue
@@ -469,12 +468,6 @@ static void do_acct_process(struct file *file)
 #endif
 	do_div(elapsed, AHZ);
 	ac.ac_btime = xtime.tv_sec - elapsed;
-	jiffies = cputime_to_jiffies(cputime_add(current->utime,
-						 current->signal->utime));
-	ac.ac_utime = encode_comp_t(jiffies_to_AHZ(jiffies));
-	jiffies = cputime_to_jiffies(cputime_add(current->stime,
-						 current->signal->stime));
-	ac.ac_stime = encode_comp_t(jiffies_to_AHZ(jiffies));
 	/* we really need to bite the bullet and change layout */
 	ac.ac_uid = current->uid;
 	ac.ac_gid = current->gid;
@@ -497,16 +490,16 @@ static void do_acct_process(struct file *file)
 	read_unlock(&tasklist_lock);
 
 	spin_lock(&current->sighand->siglock);
+	ac.ac_utime = encode_comp_t(jiffies_to_AHZ(cputime_to_jiffies(pacct->ac_utime)));
+	ac.ac_stime = encode_comp_t(jiffies_to_AHZ(cputime_to_jiffies(pacct->ac_stime)));
 	ac.ac_flag = pacct->ac_flag;
 	ac.ac_mem = encode_comp_t(pacct->ac_mem);
+	ac.ac_minflt = encode_comp_t(pacct->ac_minflt);
+	ac.ac_majflt = encode_comp_t(pacct->ac_majflt);
 	ac.ac_exitcode = pacct->ac_exitcode;
 	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 +
-				     current->min_flt);
-	ac.ac_majflt = encode_comp_t(current->signal->maj_flt +
-				     current->maj_flt);
 	ac.ac_swaps = encode_comp_t(0);
 
 	/*
@@ -532,6 +525,7 @@ static void do_acct_process(struct file *file)
 void acct_init_pacct(struct pacct_struct *pacct)
 {
 	memset(pacct, 0, sizeof(struct pacct_struct));
+	pacct->ac_utime = pacct->ac_stime = cputime_zero;
 }
 
 /**
@@ -555,7 +549,7 @@ void acct_collect(long exitcode, int group_dead)
 		up_read(&current->mm->mmap_sem);
 	}
 
-	spin_lock(&current->sighand->siglock);
+	spin_lock_irq(&current->sighand->siglock);
 	if (group_dead)
 		pacct->ac_mem = vsize / 1024;
 	if (thread_group_leader(current)) {
@@ -569,7 +563,11 @@ void acct_collect(long exitcode, int group_dead)
 		pacct->ac_flag |= ACORE;
 	if (current->flags & PF_SIGNALED)
 		pacct->ac_flag |= AXSIG;
-	spin_unlock(&current->sighand->siglock);
+	pacct->ac_utime = cputime_add(pacct->ac_utime, current->utime);
+	pacct->ac_stime = cputime_add(pacct->ac_stime, current->stime);
+	pacct->ac_minflt += current->min_flt;
+	pacct->ac_majflt += current->maj_flt;
+	spin_unlock_irq(&current->sighand->siglock);
 }
 
 /**