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author | Balbir Singh <balbir@linux.vnet.ibm.com> | 2008-09-05 18:12:23 +0200 |
---|---|---|
committer | Ingo Molnar <mingo@elte.hu> | 2008-09-05 18:14:35 +0200 |
commit | 49048622eae698e5c4ae61f7e71200f265ccc529 (patch) | |
tree | e568595fe5329e1293eafc3a3cc833dfe89ffbf2 /kernel/sched.c | |
parent | 56c7426b3951e4f35a71d695f1c982989399d6fd (diff) | |
download | kernel_samsung_smdk4412-49048622eae698e5c4ae61f7e71200f265ccc529.zip kernel_samsung_smdk4412-49048622eae698e5c4ae61f7e71200f265ccc529.tar.gz kernel_samsung_smdk4412-49048622eae698e5c4ae61f7e71200f265ccc529.tar.bz2 |
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.c | 59 |
1 files changed, 59 insertions, 0 deletions
diff --git a/kernel/sched.c b/kernel/sched.c index 9a1ddb8..1a5f73c 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -4179,6 +4179,65 @@ void account_steal_time(struct task_struct *p, cputime_t steal) } /* + * Use precise platform statistics if available: + */ +#ifdef CONFIG_VIRT_CPU_ACCOUNTING +cputime_t task_utime(struct task_struct *p) +{ + return p->utime; +} + +cputime_t task_stime(struct task_struct *p) +{ + return p->stime; +} +#else +cputime_t task_utime(struct task_struct *p) +{ + clock_t utime = cputime_to_clock_t(p->utime), + total = utime + cputime_to_clock_t(p->stime); + u64 temp; + + /* + * Use CFS's precise accounting: + */ + temp = (u64)nsec_to_clock_t(p->se.sum_exec_runtime); + + if (total) { + temp *= utime; + do_div(temp, total); + } + utime = (clock_t)temp; + + p->prev_utime = max(p->prev_utime, clock_t_to_cputime(utime)); + return p->prev_utime; +} + +cputime_t task_stime(struct task_struct *p) +{ + clock_t stime; + + /* + * Use CFS's precise accounting. (we subtract utime from + * the total, to make sure the total observed by userspace + * grows monotonically - apps rely on that): + */ + stime = nsec_to_clock_t(p->se.sum_exec_runtime) - + cputime_to_clock_t(task_utime(p)); + + if (stime >= 0) + p->prev_stime = max(p->prev_stime, clock_t_to_cputime(stime)); + + return p->prev_stime; +} +#endif + +inline cputime_t task_gtime(struct task_struct *p) +{ + return p->gtime; +} + +/* * This function gets called by the timer code, with HZ frequency. * We call it with interrupts disabled. * |