From 11b8462f7e1d25f639c88949a2746a9c2667a766 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Wed, 21 Aug 2019 21:09:07 +0200 Subject: [PATCH] posix-cpu-timers: Provide array based access to expiry cache Using struct task_cputime for the expiry cache is a pretty odd choice and comes with magic defines to rename the fields for usage in the expiry cache. struct task_cputime is basically a u64 array with 3 members, but it has distinct members. The expiry cache content is different than the content of task_cputime because expiry[PROF] = task_cputime.stime + task_cputime.utime expiry[VIRT] = task_cputime.utime expiry[SCHED] = task_cputime.sum_exec_runtime So there is no direct mapping between task_cputime and the expiry cache and the #define based remapping is just a horrible hack. Having the expiry cache array based allows further simplification of the expiry code. To avoid an all in one cleanup which is hard to review add a temporary anonymous union into struct task_cputime which allows array based access to it. That requires to reorder the members. Add a build time sanity check to validate that the members are at the same place. The union and the build time checks will be removed after conversion. Signed-off-by: Thomas Gleixner Reviewed-by: Frederic Weisbecker Link: https://lkml.kernel.org/r/20190821192921.105793824@linutronix.de --- include/linux/posix-timers.h | 24 ++++++++++++++++++------ include/linux/sched/types.h | 4 ++-- kernel/time/posix-cpu-timers.c | 12 +++++++++++- 3 files changed, 31 insertions(+), 9 deletions(-) diff --git a/include/linux/posix-timers.h b/include/linux/posix-timers.h index a3731ba15bce..ed0f6ec30aa6 100644 --- a/include/linux/posix-timers.h +++ b/include/linux/posix-timers.h @@ -65,27 +65,39 @@ static inline int clockid_to_fd(const clockid_t clk) /* * Alternate field names for struct task_cputime when used on cache * expirations. Will go away soon. + * + * stime corresponds to CLOCKCPU_PROF + * utime corresponds to CLOCKCPU_VIRT + * sum_exex_runtime corresponds to CLOCKCPU_SCHED + * + * The ordering is currently enforced so struct task_cputime and the + * expiries array in struct posix_cputimers are equivalent. */ -#define virt_exp utime #define prof_exp stime +#define virt_exp utime #define sched_exp sum_exec_runtime #ifdef CONFIG_POSIX_TIMERS /** * posix_cputimers - Container for posix CPU timer related data - * @cputime_expires: Earliest-expiration cache + * @cputime_expires: Earliest-expiration cache task_cputime based + * @expiries: Earliest-expiration cache array based * @cpu_timers: List heads to queue posix CPU timers * * Used in task_struct and signal_struct */ struct posix_cputimers { - struct task_cputime cputime_expires; - struct list_head cpu_timers[CPUCLOCK_MAX]; + /* Temporary union until all users are cleaned up */ + union { + struct task_cputime cputime_expires; + u64 expiries[CPUCLOCK_MAX]; + }; + struct list_head cpu_timers[CPUCLOCK_MAX]; }; static inline void posix_cputimers_init(struct posix_cputimers *pct) { - memset(&pct->cputime_expires, 0, sizeof(pct->cputime_expires)); + memset(&pct->expiries, 0, sizeof(pct->expiries)); INIT_LIST_HEAD(&pct->cpu_timers[0]); INIT_LIST_HEAD(&pct->cpu_timers[1]); INIT_LIST_HEAD(&pct->cpu_timers[2]); @@ -96,7 +108,7 @@ void posix_cputimers_group_init(struct posix_cputimers *pct, u64 cpu_limit); static inline void posix_cputimers_rt_watchdog(struct posix_cputimers *pct, u64 runtime) { - pct->cputime_expires.sched_exp = runtime; + pct->expiries[CPUCLOCK_SCHED] = runtime; } /* Init task static initializer */ diff --git a/include/linux/sched/types.h b/include/linux/sched/types.h index 2c5c28ddd9b2..3c3e049224ae 100644 --- a/include/linux/sched/types.h +++ b/include/linux/sched/types.h @@ -6,8 +6,8 @@ /** * struct task_cputime - collected CPU time counts - * @utime: time spent in user mode, in nanoseconds * @stime: time spent in kernel mode, in nanoseconds + * @utime: time spent in user mode, in nanoseconds * @sum_exec_runtime: total time spent on the CPU, in nanoseconds * * This structure groups together three kinds of CPU time that are tracked for @@ -15,8 +15,8 @@ * these counts together and treat all three of them in parallel. */ struct task_cputime { - u64 utime; u64 stime; + u64 utime; unsigned long long sum_exec_runtime; }; diff --git a/kernel/time/posix-cpu-timers.c b/kernel/time/posix-cpu-timers.c index 3e29d1692437..a38b6d04e8b5 100644 --- a/kernel/time/posix-cpu-timers.c +++ b/kernel/time/posix-cpu-timers.c @@ -18,13 +18,23 @@ #include "posix-timers.h" +static inline void temporary_check(void) +{ + BUILD_BUG_ON(offsetof(struct task_cputime, stime) != + CPUCLOCK_PROF * sizeof(u64)); + BUILD_BUG_ON(offsetof(struct task_cputime, utime) != + CPUCLOCK_VIRT * sizeof(u64)); + BUILD_BUG_ON(offsetof(struct task_cputime, sum_exec_runtime) != + CPUCLOCK_SCHED * sizeof(u64)); +} + static void posix_cpu_timer_rearm(struct k_itimer *timer); void posix_cputimers_group_init(struct posix_cputimers *pct, u64 cpu_limit) { posix_cputimers_init(pct); if (cpu_limit != RLIM_INFINITY) - pct->cputime_expires.prof_exp = cpu_limit * NSEC_PER_SEC; + pct->expiries[CPUCLOCK_PROF] = cpu_limit * NSEC_PER_SEC; } /*