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    Subject[PATCH 2/8] posix-cpu-timers: fix acounting delta_exec twice
    Date
    From: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>

    Currently glibc rt/tst-cpuclock2 test(*) sporadically fails because
    scheduler delta can be accounted twice from thread_group_cputimer()
    and account_group_exec_runtime().

    Finally, clock_nanosleep() wakes up before an argument. This is posix
    violation. This issue was introduced by commit d670ec1317 (posix-cpu-timers:
    Cure SMP wobbles).

    (*) http://sourceware.org/git/?p=glibc.git;a=blob;f=rt/tst-cpuclock2.c;h=6752721717f959e89c0d692b3f1ee082d507eec2;hb=HEAD

    Cc: Olivier Langlois <olivier@trillion01.com>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Cc: Frederic Weisbecker <fweisbec@gmail.com>
    Cc: Ingo Molnar <mingo@kernel.org>
    Signed-off-by: Peter Zijlstra <peterz@infradead.org>
    Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
    ---
    fs/binfmt_elf.c | 2 +-
    fs/binfmt_elf_fdpic.c | 2 +-
    include/linux/sched.h | 4 ++--
    kernel/posix-cpu-timers.c | 15 ++++++++++-----
    kernel/sched/core.c | 6 ++++--
    kernel/sched/cputime.c | 6 +++---
    6 files changed, 21 insertions(+), 14 deletions(-)

    diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
    index f8a0b0e..9f7e13a 100644
    --- a/fs/binfmt_elf.c
    +++ b/fs/binfmt_elf.c
    @@ -1326,7 +1326,7 @@ static void fill_prstatus(struct elf_prstatus *prstatus,
    * This is the record for the group leader. It shows the
    * group-wide total, not its individual thread total.
    */
    - thread_group_cputime(p, &cputime);
    + thread_group_cputime(p, true, &cputime);
    cputime_to_timeval(cputime.utime, &prstatus->pr_utime);
    cputime_to_timeval(cputime.stime, &prstatus->pr_stime);
    } else {
    diff --git a/fs/binfmt_elf_fdpic.c b/fs/binfmt_elf_fdpic.c
    index c166f32..fbcaeeb 100644
    --- a/fs/binfmt_elf_fdpic.c
    +++ b/fs/binfmt_elf_fdpic.c
    @@ -1368,7 +1368,7 @@ static void fill_prstatus(struct elf_prstatus *prstatus,
    * This is the record for the group leader. It shows the
    * group-wide total, not its individual thread total.
    */
    - thread_group_cputime(p, &cputime);
    + thread_group_cputime(p, true, &cputime);
    cputime_to_timeval(cputime.utime, &prstatus->pr_utime);
    cputime_to_timeval(cputime.stime, &prstatus->pr_stime);
    } else {
    diff --git a/include/linux/sched.h b/include/linux/sched.h
    index 178a8d9..4878579 100644
    --- a/include/linux/sched.h
    +++ b/include/linux/sched.h
    @@ -1841,7 +1841,7 @@ static inline void disable_sched_clock_irqtime(void) {}
    #endif

    extern unsigned long long
    -task_sched_runtime(struct task_struct *task);
    +task_sched_runtime(struct task_struct *task, bool add_delta);

    /* sched_exec is called by processes performing an exec */
    #ifdef CONFIG_SMP
    @@ -2502,7 +2502,7 @@ static inline void current_clr_polling(void) { }
    /*
    * Thread group CPU time accounting.
    */
    -void thread_group_cputime(struct task_struct *tsk, struct task_cputime *times);
    +void thread_group_cputime(struct task_struct *tsk, bool add_delta, struct task_cputime *times);
    void thread_group_cputimer(struct task_struct *tsk, struct task_cputime *times);

    static inline void thread_group_cputime_init(struct signal_struct *sig)
    diff --git a/kernel/posix-cpu-timers.c b/kernel/posix-cpu-timers.c
    index 42670e9..25447c5 100644
    --- a/kernel/posix-cpu-timers.c
    +++ b/kernel/posix-cpu-timers.c
    @@ -237,7 +237,7 @@ static int cpu_clock_sample(const clockid_t which_clock, struct task_struct *p,
    cpu->cpu = virt_ticks(p);
    break;
    case CPUCLOCK_SCHED:
    - cpu->sched = task_sched_runtime(p);
    + cpu->sched = task_sched_runtime(p, true);
    break;
    }
    return 0;
    @@ -267,8 +267,13 @@ void thread_group_cputimer(struct task_struct *tsk, struct task_cputime *times)
    * values through the TIMER_ABSTIME flag, therefore we have
    * to synchronize the timer to the clock every time we start
    * it.
    + *
    + * Do not add the current delta, because
    + * account_group_exec_runtime() will also this delta and we
    + * wouldn't want to double account time and get ahead of
    + * ourselves.
    */
    - thread_group_cputime(tsk, &sum);
    + thread_group_cputime(tsk, false, &sum);
    raw_spin_lock_irqsave(&cputimer->lock, flags);
    cputimer->running = 1;
    update_gt_cputime(&cputimer->cputime, &sum);
    @@ -292,15 +297,15 @@ static int cpu_clock_sample_group(const clockid_t which_clock,
    default:
    return -EINVAL;
    case CPUCLOCK_PROF:
    - thread_group_cputime(p, &cputime);
    + thread_group_cputime(p, true, &cputime);
    cpu->cpu = cputime.utime + cputime.stime;
    break;
    case CPUCLOCK_VIRT:
    - thread_group_cputime(p, &cputime);
    + thread_group_cputime(p, true, &cputime);
    cpu->cpu = cputime.utime;
    break;
    case CPUCLOCK_SCHED:
    - thread_group_cputime(p, &cputime);
    + thread_group_cputime(p, true, &cputime);
    cpu->sched = cputime.sum_exec_runtime;
    break;
    }
    diff --git a/kernel/sched/core.c b/kernel/sched/core.c
    index 58453b8..a1e823b 100644
    --- a/kernel/sched/core.c
    +++ b/kernel/sched/core.c
    @@ -2699,14 +2699,16 @@ unsigned long long task_delta_exec(struct task_struct *p)
    * In case the task is currently running, return the runtime plus current's
    * pending runtime that have not been accounted yet.
    */
    -unsigned long long task_sched_runtime(struct task_struct *p)
    +unsigned long long task_sched_runtime(struct task_struct *p, bool add_delta)
    {
    unsigned long flags;
    struct rq *rq;
    u64 ns = 0;

    rq = task_rq_lock(p, &flags);
    - ns = p->se.sum_exec_runtime + do_task_delta_exec(p, rq);
    + ns = p->se.sum_exec_runtime;
    + if (add_delta)
    + ns += do_task_delta_exec(p, rq);
    task_rq_unlock(rq, p, &flags);

    return ns;
    diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c
    index cc2dc3e..3ca432c 100644
    --- a/kernel/sched/cputime.c
    +++ b/kernel/sched/cputime.c
    @@ -277,7 +277,7 @@ static __always_inline bool steal_account_process_tick(void)
    * Accumulate raw cputime values of dead tasks (sig->[us]time) and live
    * tasks (sum on group iteration) belonging to @tsk's group.
    */
    -void thread_group_cputime(struct task_struct *tsk, struct task_cputime *times)
    +void thread_group_cputime(struct task_struct *tsk, bool add_delta, struct task_cputime *times)
    {
    struct signal_struct *sig = tsk->signal;
    cputime_t utime, stime;
    @@ -297,7 +297,7 @@ void thread_group_cputime(struct task_struct *tsk, struct task_cputime *times)
    task_cputime(t, &utime, &stime);
    times->utime += utime;
    times->stime += stime;
    - times->sum_exec_runtime += task_sched_runtime(t);
    + times->sum_exec_runtime += task_sched_runtime(t, add_delta);
    } while_each_thread(tsk, t);
    out:
    rcu_read_unlock();
    @@ -628,7 +628,7 @@ void thread_group_cputime_adjusted(struct task_struct *p, cputime_t *ut, cputime
    {
    struct task_cputime cputime;

    - thread_group_cputime(p, &cputime);
    + thread_group_cputime(p, true, &cputime);
    cputime_adjust(&cputime, &p->signal->prev_cputime, ut, st);
    }
    #endif /* !CONFIG_VIRT_CPU_ACCOUNTING_NATIVE */
    --
    1.7.1


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