Messages in this thread Patch in this message | | | Date | Tue, 17 Mar 2009 15:13:07 +0900 | From | Hidetoshi Seto <> | Subject | [PATCH] posixtimers: Fix posix clock monotonicity |
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This patch rehires task_sched_runtime() and thread_group_sched_runtime() which were removed at the time of 2.6.28-rc1.
These functions protect the sampling of clock with rq lock. This rq lock is required not to update rq->clock during the sampling. i.e. You may get ((banked runtime before update)+(delta after update)).
Signed-off-by: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com> Cc: stable@kernel.org [2.6.28.x]
--- kernel/posix-cpu-timers.c | 7 +++-- kernel/sched.c | 58 +++++++++++++++++++++++++++++++++++++++----- 2 files changed, 55 insertions(+), 10 deletions(-)
diff --git a/kernel/posix-cpu-timers.c b/kernel/posix-cpu-timers.c index 4e5288a..a65641a 100644 --- a/kernel/posix-cpu-timers.c +++ b/kernel/posix-cpu-timers.c @@ -294,7 +294,7 @@ 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 = p->se.sum_exec_runtime + task_delta_exec(p); + cpu->sched = task_sched_runtime(p); break; } return 0; @@ -310,18 +310,19 @@ static int cpu_clock_sample_group(const clockid_t which_clock, { struct task_cputime cputime; - thread_group_cputime(p, &cputime); switch (CPUCLOCK_WHICH(which_clock)) { default: return -EINVAL; case CPUCLOCK_PROF: + thread_group_cputime(p, &cputime); cpu->cpu = cputime_add(cputime.utime, cputime.stime); break; case CPUCLOCK_VIRT: + thread_group_cputime(p, &cputime); cpu->cpu = cputime.utime; break; case CPUCLOCK_SCHED: - cpu->sched = cputime.sum_exec_runtime + task_delta_exec(p); + cpu->sched = thread_group_sched_runtime(p); break; } return 0; diff --git a/kernel/sched.c b/kernel/sched.c index db66874..617d1b8 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -4066,7 +4066,23 @@ EXPORT_PER_CPU_SYMBOL(kstat); /* * Return any ns on the sched_clock that have not yet been banked in * @p in case that task is currently running. + * + * Called with task_rq_lock() held on @rq. */ +static u64 __task_delta_exec(struct task_struct *p, struct rq *rq) +{ + u64 ns = 0; + + if (task_current(rq, p)) { + update_rq_clock(rq); + ns = rq->clock - p->se.exec_start; + if ((s64)ns < 0) + ns = 0; + } + + return ns; +} + unsigned long long task_delta_exec(struct task_struct *p) { unsigned long flags; @@ -4074,16 +4090,44 @@ unsigned long long task_delta_exec(struct task_struct *p) u64 ns = 0; rq = task_rq_lock(p, &flags); + ns = __task_delta_exec(p, rq); + task_rq_unlock(rq, &flags); - if (task_current(rq, p)) { - u64 delta_exec; + return ns; +} - update_rq_clock(rq); - delta_exec = rq->clock - p->se.exec_start; - if ((s64)delta_exec > 0) - ns = delta_exec; - } +/* + * Return p->sum_exec_runtime plus any more ns on the sched_clock + * that have not yet been banked in case the task is currently running. + */ +unsigned long long task_sched_runtime(struct task_struct *p) +{ + unsigned long flags; + struct rq *rq; + u64 ns = 0; + + rq = task_rq_lock(p, &flags); + ns = p->se.sum_exec_runtime + __task_delta_exec(p, rq); + task_rq_unlock(rq, &flags); + + return ns; +} +/* + * Return sum_exec_runtime for the thread group plus any more ns on the + * sched_clock that have not yet been banked in case the task is currently + * running. + */ +unsigned long long thread_group_sched_runtime(struct task_struct *p) +{ + struct task_cputime totals; + unsigned long flags; + struct rq *rq; + u64 ns; + + rq = task_rq_lock(p, &flags); + thread_group_cputime(p, &totals); + ns = totals.sum_exec_runtime + __task_delta_exec(p, rq); task_rq_unlock(rq, &flags); return ns; -- 1.6.2.1
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