Author: mmacy
Date: Fri May 18 01:52:51 2018
New Revision: 333775
URL: https://svnweb.freebsd.org/changeset/base/333775
Log:
epoch: add non-preemptible "critical" variant
adds:
- epoch_enter_critical() - can be called inside a different epoch,
starts a section that will acquire any MTX_DEF mutexes or do
anything that might sleep.
- epoch_exit_critical() - corresponding exit call
- epoch_wait_critical() - wait variant that is guaranteed that any
threads in a section are running.
- epoch_global_critical - an epoch_wait_critical safe epoch instance
Requested by: markj
Approved by: sbruno
Modified:
head/sys/kern/subr_epoch.c
head/sys/net/if.c
head/sys/sys/epoch.h
head/sys/tests/epoch/epoch_test.c
Modified: head/sys/kern/subr_epoch.c
==============================================================================
--- head/sys/kern/subr_epoch.c Thu May 17 23:59:56 2018 (r333774)
+++ head/sys/kern/subr_epoch.c Fri May 18 01:52:51 2018 (r333775)
@@ -83,6 +83,12 @@ SYSCTL_COUNTER_U64(_kern_epoch_stats, OID_AUTO, nconte
static counter_u64_t switch_count;
SYSCTL_COUNTER_U64(_kern_epoch_stats, OID_AUTO, switches, CTLFLAG_RW,
&switch_count, "# of times a thread
voluntarily context switched in epoch_wait");
+static counter_u64_t epoch_call_count;
+SYSCTL_COUNTER_U64(_kern_epoch_stats, OID_AUTO, epoch_calls, CTLFLAG_RW,
+ &epoch_call_count, "# of times a callback
was deferred");
+static counter_u64_t epoch_call_task_count;
+SYSCTL_COUNTER_U64(_kern_epoch_stats, OID_AUTO, epoch_call_tasks, CTLFLAG_RW,
+ &epoch_call_task_count, "# of times a
callback task was run");
TAILQ_HEAD(threadlist, thread);
@@ -103,9 +109,8 @@ struct epoch_pcpu_state {
struct epoch {
struct ck_epoch e_epoch __aligned(EPOCH_ALIGN);
struct epoch_pcpu_state *e_pcpu_dom[MAXMEMDOM] __aligned(EPOCH_ALIGN);
- counter_u64_t e_frees;
- uint64_t e_free_last;
int e_idx;
+ int e_flags;
struct epoch_pcpu_state *e_pcpu[0];
};
@@ -119,7 +124,7 @@ static __read_mostly int domoffsets[MAXMEMDOM];
static __read_mostly int inited;
static __read_mostly int epoch_count;
__read_mostly epoch_t global_epoch;
-static __read_mostly epoch_t private_epoch;
+__read_mostly epoch_t global_epoch_critical;
static void epoch_call_task(void *context __unused);
@@ -161,8 +166,8 @@ epoch_init(void *arg __unused)
taskqgroup_attach_cpu(qgroup_softirq, DPCPU_ID_PTR(cpu,
epoch_cb_task), NULL, cpu, -1, "epoch call task");
}
inited = 1;
- global_epoch = epoch_alloc();
- private_epoch = epoch_alloc();
+ global_epoch = epoch_alloc(0);
+ global_epoch_critical = epoch_alloc(EPOCH_CRITICAL);
}
SYSINIT(epoch, SI_SUB_TASKQ + 1, SI_ORDER_FIRST, epoch_init, NULL);
@@ -206,7 +211,7 @@ epoch_init_legacy(epoch_t epoch)
}
epoch_t
-epoch_alloc(void)
+epoch_alloc(int flags)
{
epoch_t epoch;
@@ -215,12 +220,12 @@ epoch_alloc(void)
epoch = malloc(sizeof(struct epoch) + mp_ncpus*sizeof(void*),
M_EPOCH, M_ZERO|M_WAITOK);
ck_epoch_init(&epoch->e_epoch);
- epoch->e_frees = counter_u64_alloc(M_WAITOK);
if (usedomains)
epoch_init_numa(epoch);
else
epoch_init_legacy(epoch);
MPASS(epoch_count < MAX_EPOCHS-2);
+ epoch->e_flags = flags;
epoch->e_idx = epoch_count;
allepochs[epoch_count++] = epoch;
return (epoch);
@@ -240,11 +245,7 @@ epoch_free(epoch_t epoch)
}
#endif
allepochs[epoch->e_idx] = NULL;
- epoch_wait(private_epoch);
- /*
- * Execute any lingering callbacks
- */
- counter_u64_free(epoch->e_frees);
+ epoch_wait_critical(global_epoch_critical);
if (usedomains)
for (domain = 0; domain < vm_ndomains; domain++)
free_domain(epoch->e_pcpu_dom[domain], M_EPOCH);
@@ -289,14 +290,21 @@ epoch_enter_internal(epoch_t epoch, struct thread *td)
}
-static void
-epoch_enter_private(ck_epoch_section_t *section)
+void
+epoch_enter_critical(epoch_t epoch)
{
- struct epoch_pcpu_state *eps;
+ ck_epoch_record_t *record;
+ ck_epoch_section_t *section;
+ struct thread *td;
- MPASS(curthread->td_critnest);
- eps = private_epoch->e_pcpu[curcpu];
- ck_epoch_begin(&eps->eps_record.er_record, section);
+ section = NULL;
+ td = curthread;
+ critical_enter();
+ if (__predict_true(td->td_epochnest++ == 0))
+ section = (ck_epoch_section_t*)&td->td_epoch_section;
+
+ record = &epoch->e_pcpu[curcpu]->eps_record.er_record;
+ ck_epoch_begin(record, section);
}
void
@@ -321,14 +329,21 @@ epoch_exit_internal(epoch_t epoch, struct thread *td)
critical_exit();
}
-static void
-epoch_exit_private(ck_epoch_section_t *section)
+void
+epoch_exit_critical(epoch_t epoch)
{
- struct epoch_pcpu_state *eps;
+ ck_epoch_record_t *record;
+ ck_epoch_section_t *section;
+ struct thread *td;
- MPASS(curthread->td_critnest);
- eps = private_epoch->e_pcpu[curcpu];
- ck_epoch_end(&eps->eps_record.er_record, section);
+ section = NULL;
+ td = curthread;
+ MPASS(td->td_critnest);
+ if (__predict_true(td->td_epochnest-- == 1))
+ section = (ck_epoch_section_t*)&td->td_epoch_section;
+ record = &epoch->e_pcpu[curcpu]->eps_record.er_record;
+ ck_epoch_end(record, section);
+ critical_exit();
}
/*
@@ -517,7 +532,24 @@ epoch_wait(epoch_t epoch)
("%d residual locks held", td->td_locks - locks));
}
+static void
+epoch_block_handler_critical(struct ck_epoch *g __unused, ck_epoch_record_t *c
__unused,
+ void *arg __unused)
+{
+ cpu_spinwait();
+}
+
void
+epoch_wait_critical(epoch_t epoch)
+{
+
+ MPASS(epoch->e_flags & EPOCH_CRITICAL);
+ critical_enter();
+ ck_epoch_synchronize_wait(&epoch->e_epoch,
epoch_block_handler_critical, NULL);
+ critical_exit();
+}
+
+void
epoch_call(epoch_t epoch, epoch_context_t ctx, void (*callback)
(epoch_context_t))
{
struct epoch_pcpu_state *eps;
@@ -530,8 +562,6 @@ epoch_call(epoch_t epoch, epoch_context_t ctx, void (*
if (__predict_false(epoch == NULL))
goto boottime;
- counter_u64_add(epoch->e_frees, 1);
-
critical_enter();
*DPCPU_PTR(epoch_cb_count) += 1;
eps = epoch->e_pcpu[curcpu];
@@ -542,20 +572,18 @@ epoch_call(epoch_t epoch, epoch_context_t ctx, void (*
callback(ctx);
}
-
static void
epoch_call_task(void *arg __unused)
{
ck_stack_entry_t *cursor, *head, *next;
ck_epoch_record_t *record;
- ck_epoch_section_t section;
epoch_t epoch;
ck_stack_t cb_stack;
int i, npending, total;
ck_stack_init(&cb_stack);
critical_enter();
- epoch_enter_private(§ion);
+ epoch_enter_critical(global_epoch_critical);
for (total = i = 0; i < epoch_count; i++) {
if (__predict_false((epoch = allepochs[i]) == NULL))
continue;
@@ -565,9 +593,12 @@ epoch_call_task(void *arg __unused)
ck_epoch_poll_deferred(record, &cb_stack);
total += npending - record->n_pending;
}
- epoch_exit_private(§ion);
+ epoch_exit_critical(global_epoch_critical);
*DPCPU_PTR(epoch_cb_count) -= total;
critical_exit();
+
+ counter_u64_add(epoch_call_count, total);
+ counter_u64_add(epoch_call_task_count, 1);
head = ck_stack_batch_pop_npsc(&cb_stack);
for (cursor = head; cursor != NULL; cursor = next) {
Modified: head/sys/net/if.c
==============================================================================
--- head/sys/net/if.c Thu May 17 23:59:56 2018 (r333774)
+++ head/sys/net/if.c Fri May 18 01:52:51 2018 (r333775)
@@ -903,7 +903,7 @@ if_attachdomain(void *dummy)
{
struct ifnet *ifp;
- net_epoch = epoch_alloc();
+ net_epoch = epoch_alloc(0);
TAILQ_FOREACH(ifp, &V_ifnet, if_link)
if_attachdomain1(ifp);
}
Modified: head/sys/sys/epoch.h
==============================================================================
--- head/sys/sys/epoch.h Thu May 17 23:59:56 2018 (r333774)
+++ head/sys/sys/epoch.h Fri May 18 01:52:51 2018 (r333775)
@@ -35,7 +35,10 @@
struct epoch;
typedef struct epoch *epoch_t;
+#define EPOCH_CRITICAL 0x1
+
extern epoch_t global_epoch;
+extern epoch_t global_epoch_critical;
DPCPU_DECLARE(int, epoch_cb_count);
DPCPU_DECLARE(struct grouptask, epoch_cb_task);
@@ -45,11 +48,14 @@ struct epoch_context {
typedef struct epoch_context *epoch_context_t;
-epoch_t epoch_alloc(void);
+epoch_t epoch_alloc(int flags);
void epoch_free(epoch_t epoch);
+void epoch_enter_critical(epoch_t epoch);
void epoch_enter_internal(epoch_t epoch, struct thread *td);
+void epoch_exit_critical(epoch_t epoch);
void epoch_exit_internal(epoch_t epoch, struct thread *td);
void epoch_wait(epoch_t epoch);
+void epoch_wait_critical(epoch_t epoch);
void epoch_call(epoch_t epoch, epoch_context_t ctx, void (*callback)
(epoch_context_t));
int in_epoch(void);
Modified: head/sys/tests/epoch/epoch_test.c
==============================================================================
--- head/sys/tests/epoch/epoch_test.c Thu May 17 23:59:56 2018
(r333774)
+++ head/sys/tests/epoch/epoch_test.c Fri May 18 01:52:51 2018
(r333775)
@@ -29,6 +29,7 @@ __FBSDID("$FreeBSD$");
#include <sys/param.h>
#include <sys/types.h>
+#include <sys/proc.h>
#include <sys/counter.h>
#include <sys/epoch.h>
#include <sys/gtaskqueue.h>
@@ -138,7 +139,7 @@ test_modinit(void)
int i, error, pri_range, pri_off;
pri_range = PRI_MIN_TIMESHARE - PRI_MIN_REALTIME;
- test_epoch = epoch_alloc();
+ test_epoch = epoch_alloc(0);
for (i = 0; i < mp_ncpus*2; i++) {
etilist[i].threadid = i;
error = kthread_add(testloop, &etilist[i], NULL,
&testthreads[i],
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