Commit 0d43eb34 authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

rcu: Invert passed_quiesce and rename to cpu_no_qs 



This commit inverts the sense of the rcu_data structure's ->passed_quiesce
field and renames it to ->cpu_no_qs.  This will allow a later commit to
use an "aggregate OR" operation to test expedited as well as normal grace
periods without added overhead.

Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
parent 97c668b8

Documentation/RCU/trace.txt

+16 −16
Original line number Diff line number Diff line
@@ -56,14 +56,14 @@ rcuboost: 


The output of "cat rcu/rcu_preempt/rcudata" looks as follows:



  0!c=30455 g=30456 pq=1/0 qp=1 dt=126535/140000000000000/0 df=2002 of=4 ql=0/0 qs=N... b=10 ci=74572 nci=0 co=1131 ca=716

  1!c=30719 g=30720 pq=1/0 qp=0 dt=132007/140000000000000/0 df=1874 of=10 ql=0/0 qs=N... b=10 ci=123209 nci=0 co=685 ca=982

  2!c=30150 g=30151 pq=1/1 qp=1 dt=138537/140000000000000/0 df=1707 of=8 ql=0/0 qs=N... b=10 ci=80132 nci=0 co=1328 ca=1458

  3 c=31249 g=31250 pq=1/1 qp=0 dt=107255/140000000000000/0 df=1749 of=6 ql=0/450 qs=NRW. b=10 ci=151700 nci=0 co=509 ca=622

  4!c=29502 g=29503 pq=1/0 qp=1 dt=83647/140000000000000/0 df=965 of=5 ql=0/0 qs=N... b=10 ci=65643 nci=0 co=1373 ca=1521

  5 c=31201 g=31202 pq=1/0 qp=1 dt=70422/0/0 df=535 of=7 ql=0/0 qs=.... b=10 ci=58500 nci=0 co=764 ca=698

  6!c=30253 g=30254 pq=1/0 qp=1 dt=95363/140000000000000/0 df=780 of=5 ql=0/0 qs=N... b=10 ci=100607 nci=0 co=1414 ca=1353

  7 c=31178 g=31178 pq=1/0 qp=0 dt=91536/0/0 df=547 of=4 ql=0/0 qs=.... b=10 ci=109819 nci=0 co=1115 ca=969

  0!c=30455 g=30456 cnq=1/0:1 dt=126535/140000000000000/0 df=2002 of=4 ql=0/0 qs=N... b=10 ci=74572 nci=0 co=1131 ca=716

  1!c=30719 g=30720 cnq=1/0:0 dt=132007/140000000000000/0 df=1874 of=10 ql=0/0 qs=N... b=10 ci=123209 nci=0 co=685 ca=982

  2!c=30150 g=30151 cnq=1/1:1 dt=138537/140000000000000/0 df=1707 of=8 ql=0/0 qs=N... b=10 ci=80132 nci=0 co=1328 ca=1458

  3 c=31249 g=31250 cnq=1/1:0 dt=107255/140000000000000/0 df=1749 of=6 ql=0/450 qs=NRW. b=10 ci=151700 nci=0 co=509 ca=622

  4!c=29502 g=29503 cnq=1/0:1 dt=83647/140000000000000/0 df=965 of=5 ql=0/0 qs=N... b=10 ci=65643 nci=0 co=1373 ca=1521

  5 c=31201 g=31202 cnq=1/0:1 dt=70422/0/0 df=535 of=7 ql=0/0 qs=.... b=10 ci=58500 nci=0 co=764 ca=698

  6!c=30253 g=30254 cnq=1/0:1 dt=95363/140000000000000/0 df=780 of=5 ql=0/0 qs=N... b=10 ci=100607 nci=0 co=1414 ca=1353

  7 c=31178 g=31178 cnq=1/0:0 dt=91536/0/0 df=547 of=4 ql=0/0 qs=.... b=10 ci=109819 nci=0 co=1115 ca=969



This file has one line per CPU, or eight for this 8-CPU system.

The fields are as follows:
@@ -188,14 +188,14 @@ o "ca" is the number of RCU callbacks that have been adopted by this 
Kernels compiled with CONFIG_RCU_BOOST=y display the following from

/debug/rcu/rcu_preempt/rcudata:



  0!c=12865 g=12866 pq=1/0 qp=1 dt=83113/140000000000000/0 df=288 of=11 ql=0/0 qs=N... kt=0/O ktl=944 b=10 ci=60709 nci=0 co=748 ca=871

  1 c=14407 g=14408 pq=1/0 qp=0 dt=100679/140000000000000/0 df=378 of=7 ql=0/119 qs=NRW. kt=0/W ktl=9b6 b=10 ci=109740 nci=0 co=589 ca=485

  2 c=14407 g=14408 pq=1/0 qp=0 dt=105486/0/0 df=90 of=9 ql=0/89 qs=NRW. kt=0/W ktl=c0c b=10 ci=83113 nci=0 co=533 ca=490

  3 c=14407 g=14408 pq=1/0 qp=0 dt=107138/0/0 df=142 of=8 ql=0/188 qs=NRW. kt=0/W ktl=b96 b=10 ci=121114 nci=0 co=426 ca=290

  4 c=14405 g=14406 pq=1/0 qp=1 dt=50238/0/0 df=706 of=7 ql=0/0 qs=.... kt=0/W ktl=812 b=10 ci=34929 nci=0 co=643 ca=114

  5!c=14168 g=14169 pq=1/0 qp=0 dt=45465/140000000000000/0 df=161 of=11 ql=0/0 qs=N... kt=0/O ktl=b4d b=10 ci=47712 nci=0 co=677 ca=722

  6 c=14404 g=14405 pq=1/0 qp=0 dt=59454/0/0 df=94 of=6 ql=0/0 qs=.... kt=0/W ktl=e57 b=10 ci=55597 nci=0 co=701 ca=811

  7 c=14407 g=14408 pq=1/0 qp=1 dt=68850/0/0 df=31 of=8 ql=0/0 qs=.... kt=0/W ktl=14bd b=10 ci=77475 nci=0 co=508 ca=1042

  0!c=12865 g=12866 cnq=1/0:1 dt=83113/140000000000000/0 df=288 of=11 ql=0/0 qs=N... kt=0/O ktl=944 b=10 ci=60709 nci=0 co=748 ca=871

  1 c=14407 g=14408 cnq=1/0:0 dt=100679/140000000000000/0 df=378 of=7 ql=0/119 qs=NRW. kt=0/W ktl=9b6 b=10 ci=109740 nci=0 co=589 ca=485

  2 c=14407 g=14408 cnq=1/0:0 dt=105486/0/0 df=90 of=9 ql=0/89 qs=NRW. kt=0/W ktl=c0c b=10 ci=83113 nci=0 co=533 ca=490

  3 c=14407 g=14408 cnq=1/0:0 dt=107138/0/0 df=142 of=8 ql=0/188 qs=NRW. kt=0/W ktl=b96 b=10 ci=121114 nci=0 co=426 ca=290

  4 c=14405 g=14406 cnq=1/0:1 dt=50238/0/0 df=706 of=7 ql=0/0 qs=.... kt=0/W ktl=812 b=10 ci=34929 nci=0 co=643 ca=114

  5!c=14168 g=14169 cnq=1/0:0 dt=45465/140000000000000/0 df=161 of=11 ql=0/0 qs=N... kt=0/O ktl=b4d b=10 ci=47712 nci=0 co=677 ca=722

  6 c=14404 g=14405 cnq=1/0:0 dt=59454/0/0 df=94 of=6 ql=0/0 qs=.... kt=0/W ktl=e57 b=10 ci=55597 nci=0 co=701 ca=811

  7 c=14407 g=14408 cnq=1/0:1 dt=68850/0/0 df=31 of=8 ql=0/0 qs=.... kt=0/W ktl=14bd b=10 ci=77475 nci=0 co=508 ca=1042



This is similar to the output discussed above, but contains the following

additional fields:

kernel/rcu/tree.c

+11 −11
Original line number Diff line number Diff line
@@ -245,21 +245,21 @@ static int rcu_gp_in_progress(struct rcu_state *rsp) 
 */

void rcu_sched_qs(void)

{

	if (!__this_cpu_read(rcu_sched_data.passed_quiesce)) {

	if (__this_cpu_read(rcu_sched_data.cpu_no_qs)) {

		trace_rcu_grace_period(TPS("rcu_sched"),

				       __this_cpu_read(rcu_sched_data.gpnum),

				       TPS("cpuqs"));

		__this_cpu_write(rcu_sched_data.passed_quiesce, 1);

		__this_cpu_write(rcu_sched_data.cpu_no_qs, false);

	}

}



void rcu_bh_qs(void)

{

	if (!__this_cpu_read(rcu_bh_data.passed_quiesce)) {

	if (__this_cpu_read(rcu_bh_data.cpu_no_qs)) {

		trace_rcu_grace_period(TPS("rcu_bh"),

				       __this_cpu_read(rcu_bh_data.gpnum),

				       TPS("cpuqs"));

		__this_cpu_write(rcu_bh_data.passed_quiesce, 1);

		__this_cpu_write(rcu_bh_data.cpu_no_qs, false);

	}

}
@@ -1744,7 +1744,7 @@ static bool __note_gp_changes(struct rcu_state *rsp, struct rcu_node *rnp, 
		 */

		rdp->gpnum = rnp->gpnum;

		trace_rcu_grace_period(rsp->name, rdp->gpnum, TPS("cpustart"));

		rdp->passed_quiesce = 0;

		rdp->cpu_no_qs = true;

		rdp->rcu_qs_ctr_snap = __this_cpu_read(rcu_qs_ctr);

		rdp->core_needs_qs = !!(rnp->qsmask & rdp->grpmask);

		zero_cpu_stall_ticks(rdp);
@@ -2337,7 +2337,7 @@ rcu_report_qs_rdp(int cpu, struct rcu_state *rsp, struct rcu_data *rdp) 
	rnp = rdp->mynode;

	raw_spin_lock_irqsave(&rnp->lock, flags);

	smp_mb__after_unlock_lock();

	if ((rdp->passed_quiesce == 0 &&

	if ((rdp->cpu_no_qs &&

	     rdp->rcu_qs_ctr_snap == __this_cpu_read(rcu_qs_ctr)) ||

	    rdp->gpnum != rnp->gpnum || rnp->completed == rnp->gpnum ||

	    rdp->gpwrap) {
@@ -2348,7 +2348,7 @@ rcu_report_qs_rdp(int cpu, struct rcu_state *rsp, struct rcu_data *rdp) 
		 * We will instead need a new quiescent state that lies

		 * within the current grace period.

		 */

		rdp->passed_quiesce = 0;	/* need qs for new gp. */

		rdp->cpu_no_qs = true;	/* need qs for new gp. */

		rdp->rcu_qs_ctr_snap = __this_cpu_read(rcu_qs_ctr);

		raw_spin_unlock_irqrestore(&rnp->lock, flags);

		return;
@@ -2395,7 +2395,7 @@ rcu_check_quiescent_state(struct rcu_state *rsp, struct rcu_data *rdp) 
	 * Was there a quiescent state since the beginning of the grace

	 * period? If no, then exit and wait for the next call.

	 */

	if (!rdp->passed_quiesce &&

	if (rdp->cpu_no_qs &&

	    rdp->rcu_qs_ctr_snap == __this_cpu_read(rcu_qs_ctr))

		return;
@@ -3828,11 +3828,11 @@ static int __rcu_pending(struct rcu_state *rsp, struct rcu_data *rdp) 


	/* Is the RCU core waiting for a quiescent state from this CPU? */

	if (rcu_scheduler_fully_active &&

	    rdp->core_needs_qs && !rdp->passed_quiesce &&

	    rdp->core_needs_qs && rdp->cpu_no_qs &&

	    rdp->rcu_qs_ctr_snap == __this_cpu_read(rcu_qs_ctr)) {

		rdp->n_rp_core_needs_qs++;

	} else if (rdp->core_needs_qs &&

		   (rdp->passed_quiesce ||

		   (!rdp->cpu_no_qs ||

		    rdp->rcu_qs_ctr_snap != __this_cpu_read(rcu_qs_ctr))) {

		rdp->n_rp_report_qs++;

		return 1;
@@ -4155,7 +4155,7 @@ rcu_init_percpu_data(int cpu, struct rcu_state *rsp) 
	rdp->beenonline = true;	 /* We have now been online. */

	rdp->gpnum = rnp->completed; /* Make CPU later note any new GP. */

	rdp->completed = rnp->completed;

	rdp->passed_quiesce = false;

	rdp->cpu_no_qs = true;

	rdp->rcu_qs_ctr_snap = per_cpu(rcu_qs_ctr, cpu);

	rdp->core_needs_qs = false;

	trace_rcu_grace_period(rsp->name, rdp->gpnum, TPS("cpuonl"));

kernel/rcu/tree.h

+1 −1
Original line number Diff line number Diff line
@@ -302,7 +302,7 @@ struct rcu_data { 
					/*  is aware of having started. */

	unsigned long	rcu_qs_ctr_snap;/* Snapshot of rcu_qs_ctr to check */

					/*  for rcu_all_qs() invocations. */

	bool		passed_quiesce;	/* User-mode/idle loop etc. */

	bool		cpu_no_qs;	/* No QS yet for this CPU. */

	bool		core_needs_qs;	/* Core waits for quiesc state. */

	bool		beenonline;	/* CPU online at least once. */

	bool		gpwrap;		/* Possible gpnum/completed wrap. */

kernel/rcu/tree_plugin.h

+3 −3
Original line number Diff line number Diff line
@@ -265,11 +265,11 @@ static void rcu_preempt_ctxt_queue(struct rcu_node *rnp, struct rcu_data *rdp, 
 */

static void rcu_preempt_qs(void)

{

	if (!__this_cpu_read(rcu_data_p->passed_quiesce)) {

	if (__this_cpu_read(rcu_data_p->cpu_no_qs)) {

		trace_rcu_grace_period(TPS("rcu_preempt"),

				       __this_cpu_read(rcu_data_p->gpnum),

				       TPS("cpuqs"));

		__this_cpu_write(rcu_data_p->passed_quiesce, 1);

		__this_cpu_write(rcu_data_p->cpu_no_qs, false);

		barrier(); /* Coordinate with rcu_preempt_check_callbacks(). */

		current->rcu_read_unlock_special.b.need_qs = false;

	}
@@ -620,7 +620,7 @@ static void rcu_preempt_check_callbacks(void) 
	}

	if (t->rcu_read_lock_nesting > 0 &&

	    __this_cpu_read(rcu_data_p->core_needs_qs) &&

	    !__this_cpu_read(rcu_data_p->passed_quiesce))

	    __this_cpu_read(rcu_data_p->cpu_no_qs))

		t->rcu_read_unlock_special.b.need_qs = true;

}

kernel/rcu/tree_trace.c

+2 −2
Original line number Diff line number Diff line
@@ -117,11 +117,11 @@ static void print_one_rcu_data(struct seq_file *m, struct rcu_data *rdp) 


	if (!rdp->beenonline)

		return;

	seq_printf(m, "%3d%cc=%ld g=%ld pq=%d/%d qp=%d",

	seq_printf(m, "%3d%cc=%ld g=%ld cnq=%d/%d:%d",

		   rdp->cpu,

		   cpu_is_offline(rdp->cpu) ? '!' : ' ',

		   ulong2long(rdp->completed), ulong2long(rdp->gpnum),

		   rdp->passed_quiesce,

		   rdp->cpu_no_qs,

		   rdp->rcu_qs_ctr_snap == per_cpu(rcu_qs_ctr, rdp->cpu),

		   rdp->core_needs_qs);

	seq_printf(m, " dt=%d/%llx/%d df=%lu",

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