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Commit 8ea1de90 authored by Thomas Gleixner's avatar Thomas Gleixner
Browse files

posix-cpu-timers: Get rid of 64bit divisions 



Instead of dividing A to match the units of B it's more efficient to
multiply B to match the units of A.

Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Reviewed-by: default avatarFrederic Weisbecker <frederic@kernel.org>
Link: https://lkml.kernel.org/r/20190821192922.458286860@linutronix.de
parent 1cd07c0b

kernel/time/posix-cpu-timers.c

+14 −10
Original line number Diff line number Diff line
@@ -798,10 +798,11 @@ static void check_thread_timers(struct task_struct *tsk, 
	 */

	soft = task_rlimit(tsk, RLIMIT_RTTIME);

	if (soft != RLIM_INFINITY) {

		/* Task RT timeout is accounted in jiffies. RTTIME is usec */

		unsigned long rtim = tsk->rt.timeout * (USEC_PER_SEC / HZ);

		unsigned long hard = task_rlimit_max(tsk, RLIMIT_RTTIME);



		if (hard != RLIM_INFINITY &&

		    tsk->rt.timeout > DIV_ROUND_UP(hard, USEC_PER_SEC/HZ)) {

		if (hard != RLIM_INFINITY && rtim >= hard) {

			/*

			 * At the hard limit, we just die.

			 * No need to calculate anything else now.
@@ -813,7 +814,7 @@ static void check_thread_timers(struct task_struct *tsk, 
			__group_send_sig_info(SIGKILL, SEND_SIG_PRIV, tsk);

			return;

		}

		if (tsk->rt.timeout > DIV_ROUND_UP(soft, USEC_PER_SEC/HZ)) {

		if (rtim >= soft) {

			/*

			 * At the soft limit, send a SIGXCPU every second.

			 */
@@ -910,11 +911,13 @@ static void check_process_timers(struct task_struct *tsk, 


	soft = task_rlimit(tsk, RLIMIT_CPU);

	if (soft != RLIM_INFINITY) {

		u64 softns, ptime = samples[CPUCLOCK_PROF];

		/* RLIMIT_CPU is in seconds. Samples are nanoseconds */

		unsigned long hard = task_rlimit_max(tsk, RLIMIT_CPU);

		unsigned long psecs = div_u64(ptime, NSEC_PER_SEC);

		u64 ptime = samples[CPUCLOCK_PROF];

		u64 softns = (u64)soft * NSEC_PER_SEC;

		u64 hardns = (u64)hard * NSEC_PER_SEC;



		if (hard != RLIM_INFINITY && psecs >= hard) {

		if (hard != RLIM_INFINITY && ptime >= hardns) {

			/*

			 * At the hard limit, we just die.

			 * No need to calculate anything else now.
@@ -926,7 +929,7 @@ static void check_process_timers(struct task_struct *tsk, 
			__group_send_sig_info(SIGKILL, SEND_SIG_PRIV, tsk);

			return;

		}

		if (psecs >= soft) {

		if (ptime >= softns) {

			/*

			 * At the soft limit, send a SIGXCPU every second.

			 */
@@ -936,11 +939,12 @@ static void check_process_timers(struct task_struct *tsk, 
			}

			__group_send_sig_info(SIGXCPU, SEND_SIG_PRIV, tsk);

			if (soft < hard) {

				soft++;

				sig->rlim[RLIMIT_CPU].rlim_cur = soft;

				sig->rlim[RLIMIT_CPU].rlim_cur = soft + 1;

				softns += NSEC_PER_SEC;

			}

		}

		softns = soft * NSEC_PER_SEC;



		/* Update the expiry cache */

		if (softns < pct->bases[CPUCLOCK_PROF].nextevt)

			pct->bases[CPUCLOCK_PROF].nextevt = softns;

	}