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busdma_bounce: Use a simple kproc to invoke deferred requests.

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Rather than using a software interrupt with a single handler, just
create a dedicated kernel process woken up with a simple wakeup().

Reviewed by:	imp
Sponsored by:	Netflix
Differential Revision:	https://reviews.freebsd.org/D34965
This commit is contained in:
John Baldwin 2022-04-21 10:40:35 -07:00
parent c7aa0304d5
commit d11f5d4762
1 changed files with 39 additions and 28 deletions
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67
sys/kern/subr_busdma_bounce.c
View File

@ -45,6 +45,9 @@
* - dmat_lockarg()
*/
#include <sys/kthread.h>
#include <sys/sched.h>
struct bounce_page {
vm_offset_t vaddr; /* kva of bounce buffer */
bus_addr_t busaddr; /* Physical address */
@ -87,13 +90,13 @@ static int busdma_zonecount;
static STAILQ_HEAD(, bounce_zone) bounce_zone_list;
static STAILQ_HEAD(, bus_dmamap) bounce_map_waitinglist;
static STAILQ_HEAD(, bus_dmamap) bounce_map_callbacklist;
static void *busdma_ih;
static MALLOC_DEFINE(M_BOUNCE, "bounce", "busdma bounce pages");
SYSCTL_INT(_hw_busdma, OID_AUTO, total_bpages, CTLFLAG_RD, &total_bpages, 0,
"Total bounce pages");
static void busdma_thread(void *);
static int reserve_bounce_pages(bus_dma_tag_t dmat, bus_dmamap_t map,
int commit);
@ -152,6 +155,7 @@ static int
alloc_bounce_zone(bus_dma_tag_t dmat)
{
struct bounce_zone *bz;
bool start_thread;
/* Check to see if we already have a suitable zone */
STAILQ_FOREACH(bz, &bounce_zone_list, links) {
@ -183,6 +187,7 @@ alloc_bounce_zone(bus_dma_tag_t dmat)
busdma_zonecount++;
snprintf(bz->lowaddrid, sizeof(bz->lowaddrid), "%#jx",
(uintmax_t)bz->lowaddr);
start_thread = STAILQ_EMPTY(&bounce_zone_list);
STAILQ_INSERT_TAIL(&bounce_zone_list, bz, links);
dmat->bounce_zone = bz;
@ -232,6 +237,11 @@ alloc_bounce_zone(bus_dma_tag_t dmat)
"memory domain");
#endif
if (start_thread) {
if (kproc_create(busdma_thread, NULL, NULL, 0, 0, "busdma") !=
0)
printf("failed to create busdma thread");
}
return (0);
}
@ -373,7 +383,7 @@ free_bounce_page(bus_dma_tag_t dmat, struct bounce_page *bpage)
{
struct bus_dmamap *map;
struct bounce_zone *bz;
bool schedule_swi;
bool schedule_thread;
bz = dmat->bounce_zone;
bpage->datavaddr = 0;
@ -388,7 +398,7 @@ free_bounce_page(bus_dma_tag_t dmat, struct bounce_page *bpage)
bpage->busaddr &= ~PAGE_MASK;
}
schedule_swi = false;
schedule_thread = false;
mtx_lock(&bounce_lock);
STAILQ_INSERT_HEAD(&bz->bounce_page_list, bpage, links);
bz->free_bpages++;
@ -399,40 +409,41 @@ free_bounce_page(bus_dma_tag_t dmat, struct bounce_page *bpage)
STAILQ_INSERT_TAIL(&bounce_map_callbacklist,
map, links);
bz->total_deferred++;
schedule_swi = true;
schedule_thread = true;
}
}
mtx_unlock(&bounce_lock);
if (schedule_swi)
swi_sched(busdma_ih, 0);
if (schedule_thread)
wakeup(&bounce_map_callbacklist);
}
static void
busdma_swi(void *dummy __unused)
busdma_thread(void *dummy __unused)
{
STAILQ_HEAD(, bus_dmamap) callbacklist;
bus_dma_tag_t dmat;
struct bus_dmamap *map;
struct bus_dmamap *map, *nmap;
mtx_lock(&bounce_lock);
while ((map = STAILQ_FIRST(&bounce_map_callbacklist)) != NULL) {
STAILQ_REMOVE_HEAD(&bounce_map_callbacklist, links);
mtx_unlock(&bounce_lock);
dmat = map->dmat;
dmat_lockfunc(dmat)(dmat_lockfuncarg(dmat), BUS_DMA_LOCK);
bus_dmamap_load_mem(map->dmat, map, &map->mem, map->callback,
map->callback_arg, BUS_DMA_WAITOK);
dmat_lockfunc(dmat)(dmat_lockfuncarg(dmat), BUS_DMA_UNLOCK);
thread_lock(curthread);
sched_prio(curthread, PI_SWI(SWI_BUSDMA));
thread_unlock(curthread);
for (;;) {
mtx_lock(&bounce_lock);
}
mtx_unlock(&bounce_lock);
}
while (STAILQ_EMPTY(&bounce_map_callbacklist))
mtx_sleep(&bounce_map_callbacklist, &bounce_lock, 0,
"-", 0);
STAILQ_INIT(&callbacklist);
STAILQ_CONCAT(&callbacklist, &bounce_map_callbacklist);
mtx_unlock(&bounce_lock);
static void
start_busdma_swi(void *dummy __unused)
{
if (swi_add(NULL, "busdma", busdma_swi, NULL, SWI_BUSDMA, INTR_MPSAFE,
&busdma_ih))
panic("died while creating busdma swi ithread");
STAILQ_FOREACH_SAFE(map, &callbacklist, links, nmap) {
dmat = map->dmat;
dmat_lockfunc(dmat)(dmat_lockfuncarg(dmat),
BUS_DMA_LOCK);
bus_dmamap_load_mem(map->dmat, map, &map->mem,
map->callback, map->callback_arg, BUS_DMA_WAITOK);
dmat_lockfunc(dmat)(dmat_lockfuncarg(dmat),
BUS_DMA_UNLOCK);
}
}
}
SYSINIT(start_busdma_swi, SI_SUB_SOFTINTR, SI_ORDER_ANY, start_busdma_swi,
NULL);