Author: hselasky Date: Wed Aug 19 12:23:05 2020 New Revision: 364381 URL: https://svnweb.freebsd.org/changeset/base/364381
Log: MFC r364019: Add full support support for dynamic allocation and freeing of epoch's. Make sure to reclaim epoch structures when they are freed to support dynamic allocation and freeing of epoch structures. While at it, move the 64 supported epoch control structures to the static memory domain. This overall simplifies the management and debugging of system epoch's. Reviewed by: kib, markj Differential Revision: https://reviews.freebsd.org/D25960 Sponsored by: Mellanox Technologies Modified: stable/12/sys/kern/subr_epoch.c Directory Properties: stable/12/ (props changed) Modified: stable/12/sys/kern/subr_epoch.c ============================================================================== --- stable/12/sys/kern/subr_epoch.c Wed Aug 19 12:16:11 2020 (r364380) +++ stable/12/sys/kern/subr_epoch.c Wed Aug 19 12:23:05 2020 (r364381) @@ -54,8 +54,6 @@ __FBSDID("$FreeBSD$"); #include <ck_epoch.h> -static MALLOC_DEFINE(M_EPOCH, "epoch", "epoch based reclamation"); - #ifdef __amd64__ #define EPOCH_ALIGN CACHE_LINE_SIZE*2 #else @@ -76,7 +74,7 @@ typedef struct epoch_record { struct epoch { struct ck_epoch e_epoch __aligned(EPOCH_ALIGN); epoch_record_t e_pcpu_record; - int e_idx; + int e_in_use; int e_flags; /* fields above are part of KBI and cannot be modified */ struct sx e_drain_sx; @@ -123,19 +121,23 @@ TAILQ_HEAD (threadlist, thread); CK_STACK_CONTAINER(struct ck_epoch_entry, stack_entry, ck_epoch_entry_container) -epoch_t allepochs[MAX_EPOCHS]; +static struct epoch epoch_array[MAX_EPOCHS]; DPCPU_DEFINE(struct grouptask, epoch_cb_task); DPCPU_DEFINE(int, epoch_cb_count); static __read_mostly int inited; -static __read_mostly int epoch_count; __read_mostly epoch_t global_epoch; __read_mostly epoch_t global_epoch_preempt; static void epoch_call_task(void *context __unused); static uma_zone_t pcpu_zone_record; +static struct sx epoch_sx; + +#define EPOCH_LOCK() sx_xlock(&epoch_sx) +#define EPOCH_UNLOCK() sx_xunlock(&epoch_sx) + static void epoch_init(void *arg __unused) { @@ -158,6 +160,7 @@ epoch_init(void *arg __unused) DPCPU_ID_PTR(cpu, epoch_cb_task), NULL, cpu, -1, "epoch call task"); } + sx_init(&epoch_sx, "epoch-sx"); inited = 1; global_epoch = epoch_alloc(0); global_epoch_preempt = epoch_alloc(EPOCH_PREEMPT); @@ -203,18 +206,47 @@ epoch_t epoch_alloc(int flags) { epoch_t epoch; + int i; + MPASS(name != NULL); + if (__predict_false(!inited)) panic("%s called too early in boot", __func__); - epoch = malloc(sizeof(struct epoch), M_EPOCH, M_ZERO | M_WAITOK); + + EPOCH_LOCK(); + + /* + * Find a free index in the epoch array. If no free index is + * found, try to use the index after the last one. + */ + for (i = 0;; i++) { + /* + * If too many epochs are currently allocated, + * return NULL. + */ + if (i == MAX_EPOCHS) { + epoch = NULL; + goto done; + } + if (epoch_array[i].e_in_use == 0) + break; + } + + epoch = epoch_array + i; ck_epoch_init(&epoch->e_epoch); epoch_ctor(epoch); - MPASS(epoch_count < MAX_EPOCHS - 2); epoch->e_flags = flags; - epoch->e_idx = epoch_count; sx_init(&epoch->e_drain_sx, "epoch-drain-sx"); mtx_init(&epoch->e_drain_mtx, "epoch-drain-mtx", NULL, MTX_DEF); - allepochs[epoch_count++] = epoch; + + /* + * Set e_in_use last, because when this field is set the + * epoch_call_task() function will start scanning this epoch + * structure. + */ + atomic_store_rel_int(&epoch->e_in_use, 1); +done: + EPOCH_UNLOCK(); return (epoch); } @@ -222,13 +254,24 @@ void epoch_free(epoch_t epoch) { + EPOCH_LOCK(); + + MPASS(epoch->e_in_use != 0); + epoch_drain_callbacks(epoch); - allepochs[epoch->e_idx] = NULL; + + atomic_store_rel_int(&epoch->e_in_use, 0); + /* + * Make sure the epoch_call_task() function see e_in_use equal + * to zero, by calling epoch_wait() on the global_epoch: + */ epoch_wait(global_epoch); uma_zfree_pcpu(pcpu_zone_record, epoch->e_pcpu_record); mtx_destroy(&epoch->e_drain_mtx); sx_destroy(&epoch->e_drain_sx); - free(epoch, M_EPOCH); + memset(epoch, 0, sizeof(*epoch)); + + EPOCH_UNLOCK(); } static epoch_record_t @@ -592,8 +635,10 @@ epoch_call_task(void *arg __unused) ck_stack_init(&cb_stack); critical_enter(); epoch_enter(global_epoch); - for (total = i = 0; i < epoch_count; i++) { - if (__predict_false((epoch = allepochs[i]) == NULL)) + for (total = i = 0; i != MAX_EPOCHS; i++) { + epoch = epoch_array + i; + if (__predict_false( + atomic_load_acq_int(&epoch->e_in_use) == 0)) continue; er = epoch_currecord(epoch); record = &er->er_record; _______________________________________________ svn-src-all@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/svn-src-all To unsubscribe, send any mail to "svn-src-all-unsubscr...@freebsd.org"
