Commit 11b8462f authored by Thomas Gleixner's avatar Thomas Gleixner
Browse files

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: default avatarThomas Gleixner <tglx@linutronix.de>
Reviewed-by: default avatarFrederic Weisbecker <frederic@kernel.org>
Link: https://lkml.kernel.org/r/20190821192921.105793824@linutronix.de
parent 3a245c0f

include/linux/posix-timers.h

+18 −6
Original line number Original line Diff line number Diff line
@@ -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

 * Alternate field names for struct task_cputime when used on cache

 * expirations. Will go away soon.

 * 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 prof_exp			stime

#define virt_exp			utime

#define sched_exp			sum_exec_runtime

#define sched_exp			sum_exec_runtime





#ifdef CONFIG_POSIX_TIMERS

#ifdef CONFIG_POSIX_TIMERS

/**

/**

 * posix_cputimers - Container for posix CPU timer related data

 * 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

 * @cpu_timers:		List heads to queue posix CPU timers

 *

 *

 * Used in task_struct and signal_struct

 * Used in task_struct and signal_struct

 */

 */

struct posix_cputimers {

struct posix_cputimers {

	/* Temporary union until all users are cleaned up */

	union {

		struct task_cputime	cputime_expires;

		struct task_cputime	cputime_expires;

		u64			expiries[CPUCLOCK_MAX];

	};

	struct list_head		cpu_timers[CPUCLOCK_MAX];

	struct list_head		cpu_timers[CPUCLOCK_MAX];

};

};





static inline void posix_cputimers_init(struct posix_cputimers *pct)

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[0]);

	INIT_LIST_HEAD(&pct->cpu_timers[1]);

	INIT_LIST_HEAD(&pct->cpu_timers[1]);

	INIT_LIST_HEAD(&pct->cpu_timers[2]);

	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,

static inline void posix_cputimers_rt_watchdog(struct posix_cputimers *pct,

					       u64 runtime)

					       u64 runtime)

{

{

	pct->cputime_expires.sched_exp = runtime;

	pct->expiries[CPUCLOCK_SCHED] = runtime;

}

}





/* Init task static initializer */

/* Init task static initializer */

include/linux/sched/types.h

+2 −2
Original line number Original line Diff line number Diff line
@@ -6,8 +6,8 @@ 




/**

/**

 * struct task_cputime - collected CPU time counts

 * struct task_cputime - collected CPU time counts

 * @utime:		time spent in user mode, in nanoseconds

 * @stime:		time spent in kernel 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

 * @sum_exec_runtime:	total time spent on the CPU, in nanoseconds

 *

 *

 * This structure groups together three kinds of CPU time that are tracked for

 * 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.

 * these counts together and treat all three of them in parallel.

 */

 */

struct task_cputime {

struct task_cputime {

	u64				utime;

	u64				stime;

	u64				stime;

	u64				utime;

	unsigned long long		sum_exec_runtime;

	unsigned long long		sum_exec_runtime;

};

};

kernel/time/posix-cpu-timers.c

+11 −1
Original line number Original line Diff line number Diff line
@@ -18,13 +18,23 @@ 




#include "posix-timers.h"

#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);

static void posix_cpu_timer_rearm(struct k_itimer *timer);





void posix_cputimers_group_init(struct posix_cputimers *pct, u64 cpu_limit)

void posix_cputimers_group_init(struct posix_cputimers *pct, u64 cpu_limit)

{

{

	posix_cputimers_init(pct);

	posix_cputimers_init(pct);

	if (cpu_limit != RLIM_INFINITY)

	if (cpu_limit != RLIM_INFINITY)

		pct->cputime_expires.prof_exp = cpu_limit * NSEC_PER_SEC;

		pct->expiries[CPUCLOCK_PROF] = cpu_limit * NSEC_PER_SEC;

}

}





/*

/*

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