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rcu: Add full-sized polling for start_poll_expedited() 

The start_poll_synchronize_rcu_expedited() API compresses the combined
expedited and normal grace-period states into a single unsigned long,
which conserves storage, but can miss grace periods in certain cases
involving overlapping normal and expedited grace periods.  Missing the
occasional grace period is usually not a problem, but there are use
cases that care about each and every grace period.

This commit therefore adds yet another member of the
full-state RCU grace-period polling API, which is the
start_poll_synchronize_rcu_expedited_full() function.  This uses up to
three times the storage (rcu_gp_oldstate structure instead of unsigned
long), but is guaranteed not to miss grace periods.

[ paulmck: Apply feedback from kernel test robot and Julia Lawall. ]

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit is contained in:
Paul E. McKenney 2022-08-03 12:38:51 -07:00
parent 76ea364161
commit 6c502b14ba
4 changed files with 65 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
include/linux/rcutiny.h
View File

@ -49,6 +49,11 @@ static inline unsigned long start_poll_synchronize_rcu_expedited(void)
return start_poll_synchronize_rcu();
}
static inline void start_poll_synchronize_rcu_expedited_full(struct rcu_gp_oldstate *rgosp)
{
rgosp->rgos_norm = start_poll_synchronize_rcu_expedited();
}
static inline void cond_synchronize_rcu_expedited(unsigned long oldstate)
{
cond_synchronize_rcu(oldstate);

1
include/linux/rcutree.h
View File

@ -48,6 +48,7 @@ struct rcu_gp_oldstate {
};
unsigned long start_poll_synchronize_rcu_expedited(void);
void start_poll_synchronize_rcu_expedited_full(struct rcu_gp_oldstate *rgosp);
void cond_synchronize_rcu_expedited(unsigned long oldstate);
unsigned long get_state_synchronize_rcu(void);
void get_state_synchronize_rcu_full(struct rcu_gp_oldstate *rgosp);

51
kernel/rcu/rcutorture.c
View File

@ -89,6 +89,7 @@ torture_param(bool, gp_normal, false, "Use normal (non-expedited) GP wait primit
torture_param(bool, gp_poll, false, "Use polling GP wait primitives");
torture_param(bool, gp_poll_exp, false, "Use polling expedited GP wait primitives");
torture_param(bool, gp_poll_full, false, "Use polling full-state GP wait primitives");
torture_param(bool, gp_poll_exp_full, false, "Use polling full-state expedited GP wait primitives");
torture_param(bool, gp_sync, false, "Use synchronous GP wait primitives");
torture_param(int, irqreader, 1, "Allow RCU readers from irq handlers");
torture_param(int, leakpointer, 0, "Leak pointer dereferences from readers");
@ -201,12 +202,14 @@ static int rcu_torture_writer_state;
#define RTWS_POLL_GET 9
#define RTWS_POLL_GET_FULL 10
#define RTWS_POLL_GET_EXP 11
#define RTWS_POLL_WAIT 12
#define RTWS_POLL_WAIT_FULL 13
#define RTWS_POLL_WAIT_EXP 14
#define RTWS_SYNC 15
#define RTWS_STUTTER 16
#define RTWS_STOPPING 17
#define RTWS_POLL_GET_EXP_FULL 12
#define RTWS_POLL_WAIT 13
#define RTWS_POLL_WAIT_FULL 14
#define RTWS_POLL_WAIT_EXP 15
#define RTWS_POLL_WAIT_EXP_FULL 16
#define RTWS_SYNC 17
#define RTWS_STUTTER 18
#define RTWS_STOPPING 19
static const char * const rcu_torture_writer_state_names[] = {
"RTWS_FIXED_DELAY",
"RTWS_DELAY",
@ -220,9 +223,11 @@ static const char * const rcu_torture_writer_state_names[] = {
"RTWS_POLL_GET",
"RTWS_POLL_GET_FULL",
"RTWS_POLL_GET_EXP",
"RTWS_POLL_GET_EXP_FULL",
"RTWS_POLL_WAIT",
"RTWS_POLL_WAIT_FULL",
"RTWS_POLL_WAIT_EXP",
"RTWS_POLL_WAIT_EXP_FULL",
"RTWS_SYNC",
"RTWS_STUTTER",
"RTWS_STOPPING",
@ -337,6 +342,7 @@ struct rcu_torture_ops {
void (*exp_sync)(void);
unsigned long (*get_gp_state_exp)(void);
unsigned long (*start_gp_poll_exp)(void);
void (*start_gp_poll_exp_full)(struct rcu_gp_oldstate *rgosp);
bool (*poll_gp_state_exp)(unsigned long oldstate);
void (*cond_sync_exp)(unsigned long oldstate);
unsigned long (*get_gp_state)(void);
@ -528,6 +534,7 @@ static struct rcu_torture_ops rcu_ops = {
.cond_sync = cond_synchronize_rcu,
.get_gp_state_exp = get_state_synchronize_rcu,
.start_gp_poll_exp = start_poll_synchronize_rcu_expedited,
.start_gp_poll_exp_full = start_poll_synchronize_rcu_expedited_full,
.poll_gp_state_exp = poll_state_synchronize_rcu,
.cond_sync_exp = cond_synchronize_rcu_expedited,
.call = call_rcu,
@ -1169,13 +1176,14 @@ static int nsynctypes;
static void rcu_torture_write_types(void)
{
bool gp_cond1 = gp_cond, gp_cond_exp1 = gp_cond_exp, gp_exp1 = gp_exp;
bool gp_poll_exp1 = gp_poll_exp, gp_normal1 = gp_normal, gp_poll1 = gp_poll;
bool gp_poll_full1 = gp_poll_full, gp_sync1 = gp_sync;
bool gp_poll_exp1 = gp_poll_exp, gp_poll_exp_full1 = gp_poll_exp_full;
bool gp_normal1 = gp_normal, gp_poll1 = gp_poll, gp_poll_full1 = gp_poll_full;
bool gp_sync1 = gp_sync;
/* Initialize synctype[] array. If none set, take default. */
if (!gp_cond1 && !gp_cond_exp1 && !gp_exp1 && !gp_poll_exp &&
if (!gp_cond1 && !gp_cond_exp1 && !gp_exp1 && !gp_poll_exp && !gp_poll_exp_full1 &&
!gp_normal1 && !gp_poll1 && !gp_poll_full1 && !gp_sync1)
gp_cond1 = gp_cond_exp1 = gp_exp1 = gp_poll_exp1 =
gp_cond1 = gp_cond_exp1 = gp_exp1 = gp_poll_exp1 = gp_poll_exp_full1 =
gp_normal1 = gp_poll1 = gp_poll_full1 = gp_sync1 = true;
if (gp_cond1 && cur_ops->get_gp_state && cur_ops->cond_sync) {
synctype[nsynctypes++] = RTWS_COND_GET;
@ -1219,6 +1227,13 @@ static void rcu_torture_write_types(void)
} else if (gp_poll_exp && (!cur_ops->start_gp_poll_exp || !cur_ops->poll_gp_state_exp)) {
pr_alert("%s: gp_poll_exp without primitives.\n", __func__);
}
if (gp_poll_exp_full1 && cur_ops->start_gp_poll_exp_full && cur_ops->poll_gp_state_full) {
synctype[nsynctypes++] = RTWS_POLL_GET_EXP_FULL;
pr_info("%s: Testing polling full-state expedited GPs.\n", __func__);
} else if (gp_poll_exp_full &&
(!cur_ops->start_gp_poll_exp_full || !cur_ops->poll_gp_state_full)) {
pr_alert("%s: gp_poll_exp_full without primitives.\n", __func__);
}
if (gp_sync1 && cur_ops->sync) {
synctype[nsynctypes++] = RTWS_SYNC;
pr_info("%s: Testing normal GPs.\n", __func__);
@ -1408,6 +1423,15 @@ rcu_torture_writer(void *arg)
&rand);
rcu_torture_pipe_update(old_rp);
break;
case RTWS_POLL_GET_EXP_FULL:
rcu_torture_writer_state = RTWS_POLL_GET_EXP_FULL;
cur_ops->start_gp_poll_exp_full(&gp_snap_full);
rcu_torture_writer_state = RTWS_POLL_WAIT_EXP_FULL;
while (!cur_ops->poll_gp_state_full(&gp_snap_full))
torture_hrtimeout_jiffies(torture_random(&rand) % 16,
&rand);
rcu_torture_pipe_update(old_rp);
break;
case RTWS_SYNC:
rcu_torture_writer_state = RTWS_SYNC;
do_rtws_sync(&rand, cur_ops->sync);
@ -1537,6 +1561,13 @@ rcu_torture_fakewriter(void *arg)
&rand);
}
break;
case RTWS_POLL_GET_EXP_FULL:
cur_ops->start_gp_poll_exp_full(&gp_snap_full);
while (!cur_ops->poll_gp_state_full(&gp_snap_full)) {
torture_hrtimeout_jiffies(torture_random(&rand) % 16,
&rand);
}
break;
case RTWS_SYNC:
cur_ops->sync();
break;

18
kernel/rcu/tree_exp.h
View File

@ -1027,6 +1027,24 @@ unsigned long start_poll_synchronize_rcu_expedited(void)
}
EXPORT_SYMBOL_GPL(start_poll_synchronize_rcu_expedited);
/**
* start_poll_synchronize_rcu_expedited_full - Take a full snapshot and start expedited grace period
* @rgosp: Place to put snapshot of grace-period state
*
* Places the normal and expedited grace-period states in rgosp. This
* state value can be passed to a later call to cond_synchronize_rcu_full()
* or poll_state_synchronize_rcu_full() to determine whether or not a
* grace period (whether normal or expedited) has elapsed in the meantime.
* If the needed expedited grace period is not already slated to start,
* initiates that grace period.
*/
void start_poll_synchronize_rcu_expedited_full(struct rcu_gp_oldstate *rgosp)
{
get_state_synchronize_rcu_full(rgosp);
(void)start_poll_synchronize_rcu_expedited();
}
EXPORT_SYMBOL_GPL(start_poll_synchronize_rcu_expedited_full);
/**
* cond_synchronize_rcu_expedited - Conditionally wait for an expedited RCU grace period
*