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authorBalbir Singh <balbir@linux.vnet.ibm.com>2008-09-05 12:12:23 -0400
committerIngo Molnar <mingo@elte.hu>2008-09-05 12:14:35 -0400
commit49048622eae698e5c4ae61f7e71200f265ccc529 (patch)
treee568595fe5329e1293eafc3a3cc833dfe89ffbf2 /kernel/sched.c
parent56c7426b3951e4f35a71d695f1c982989399d6fd (diff)
sched: fix process time monotonicity
Spencer reported a problem where utime and stime were going negative despite the fixes in commit b27f03d4bdc145a09fb7b0c0e004b29f1ee555fa. The suspected reason for the problem is that signal_struct maintains it's own utime and stime (of exited tasks), these are not updated using the new task_utime() routine, hence sig->utime can go backwards and cause the same problem to occur (sig->utime, adds tsk->utime and not task_utime()). This patch fixes the problem TODO: using max(task->prev_utime, derived utime) works for now, but a more generic solution is to implement cputime_max() and use the cputime_gt() function for comparison. Reported-by: spencer@bluehost.com Signed-off-by: Balbir Singh <balbir@linux.vnet.ibm.com> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel/sched.c')
-rw-r--r--kernel/sched.c59
1 files changed, 59 insertions, 0 deletions
diff --git a/kernel/sched.c b/kernel/sched.c
index 9a1ddb84e26..1a5f73c1fcd 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -4179,6 +4179,65 @@ void account_steal_time(struct task_struct *p, cputime_t steal)
4179} 4179}
4180 4180
4181/* 4181/*
4182 * Use precise platform statistics if available:
4183 */
4184#ifdef CONFIG_VIRT_CPU_ACCOUNTING
4185cputime_t task_utime(struct task_struct *p)
4186{
4187 return p->utime;
4188}
4189
4190cputime_t task_stime(struct task_struct *p)
4191{
4192 return p->stime;
4193}
4194#else
4195cputime_t task_utime(struct task_struct *p)
4196{
4197 clock_t utime = cputime_to_clock_t(p->utime),
4198 total = utime + cputime_to_clock_t(p->stime);
4199 u64 temp;
4200
4201 /*
4202 * Use CFS's precise accounting:
4203 */
4204 temp = (u64)nsec_to_clock_t(p->se.sum_exec_runtime);
4205
4206 if (total) {
4207 temp *= utime;
4208 do_div(temp, total);
4209 }
4210 utime = (clock_t)temp;
4211
4212 p->prev_utime = max(p->prev_utime, clock_t_to_cputime(utime));
4213 return p->prev_utime;
4214}
4215
4216cputime_t task_stime(struct task_struct *p)
4217{
4218 clock_t stime;
4219
4220 /*
4221 * Use CFS's precise accounting. (we subtract utime from
4222 * the total, to make sure the total observed by userspace
4223 * grows monotonically - apps rely on that):
4224 */
4225 stime = nsec_to_clock_t(p->se.sum_exec_runtime) -
4226 cputime_to_clock_t(task_utime(p));
4227
4228 if (stime >= 0)
4229 p->prev_stime = max(p->prev_stime, clock_t_to_cputime(stime));
4230
4231 return p->prev_stime;
4232}
4233#endif
4234
4235inline cputime_t task_gtime(struct task_struct *p)
4236{
4237 return p->gtime;
4238}
4239
4240/*
4182 * This function gets called by the timer code, with HZ frequency. 4241 * This function gets called by the timer code, with HZ frequency.
4183 * We call it with interrupts disabled. 4242 * We call it with interrupts disabled.
4184 * 4243 *