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vdire: plug the remaining vcl temperature change races #4259

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vdire: plug the remaining vcl temperature change races #4259

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103 changes: 93 additions & 10 deletions bin/varnishd/cache/cache_vcl.c
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Original file line number Diff line number Diff line change
Expand Up @@ -436,6 +436,36 @@ vdire_end_iter(struct vdire *vdire)
vcldir_retire(vdir, temp);
}

/*
* like vdire_start_iter, but also prepare for backend_event_*()
* by setting the checkpoint
*/
static void
vdire_start_event(struct vdire *vdire, const struct vcltemp *temp)
{

CHECK_OBJ_NOTNULL(vdire, VDIRE_MAGIC);
AN(temp);

Lck_AssertHeld(vdire->mtx);

// https://github.com/varnishcache/varnish-cache/pull/4142#issuecomment-2593091097
ASSERT_CLI();

AZ(vdire->checkpoint);
vdire->checkpoint = VTAILQ_LAST(&vdire->directors, vcldir_head);
AN(vdire->tempp);
*vdire->tempp = temp;
vdire->iterating++;
}

static void
vdire_end_event(struct vdire *vdire)
{
vdire->checkpoint = NULL;
vdire_end_iter(vdire);
}

// if there are no iterators, remove from directors and retire
// otherwise put on resigning list to work when iterators end
void
Expand Down Expand Up @@ -557,8 +587,13 @@ VCL_IterDirector(struct cli *cli, const char *pat,
return (found);
}

/*
* vdire_start_event() must have been called before
*
* send event to directors pre checkpoint
*/
static void
vcl_BackendEvent(const struct vcl *vcl, enum vcl_event_e e)
backend_event_base(const struct vcl *vcl, enum vcl_event_e e)
{
struct vcldir *vdir;
struct vdire *vdire;
Expand All @@ -567,11 +602,54 @@ vcl_BackendEvent(const struct vcl *vcl, enum vcl_event_e e)
CHECK_OBJ_NOTNULL(vcl, VCL_MAGIC);
AZ(vcl->busy);
vdire = vcl->vdire;
AN(vdire->iterating);

vdire_start_iter(vdire);
VTAILQ_FOREACH(vdir, &vdire->directors, directors_list)
if (vdire->checkpoint == NULL)
return;

VTAILQ_FOREACH(vdir, &vdire->directors, directors_list) {
VDI_Event(vdir->dir, e);
vdire_end_iter(vdire);
if (vdir == vdire->checkpoint)
break;
}
}

/*
* vdire_start_event() must have been called before
*
* set a new temperature.
* send event to directors added post checkpoint, but before
* the new temperature
*/
static void
backend_event_delta(const struct vcl *vcl, enum vcl_event_e e, const struct vcltemp *temp)
{
struct vcldir *vdir, *end;
struct vdire *vdire;

ASSERT_CLI();
CHECK_OBJ_NOTNULL(vcl, VCL_MAGIC);
AZ(vcl->busy);
vdire = vcl->vdire;
AN(temp);
AN(vdire->iterating);

Lck_Lock(vdire->mtx);
if (vdire->checkpoint == NULL)
vdir = VTAILQ_FIRST(&vdire->directors);
else
vdir = VTAILQ_NEXT(vdire->checkpoint, directors_list);
AN(vdire->tempp);
*vdire->tempp = temp;
end = VTAILQ_LAST(&vdire->directors, vcldir_head);
Lck_Unlock(vdire->mtx);

while (vdir != NULL) {
VDI_Event(vdir->dir, e);
if (vdir == end)
break;
vdir = VTAILQ_NEXT(vdire->checkpoint, directors_list);
}
}

static void
Expand Down Expand Up @@ -742,10 +820,12 @@ vcl_set_state(struct vcl *vcl, const char *state, struct vsb **msg)
break;
if (vcl->busy == 0 && vcl->temp->is_warm) {
Lck_Lock(&vcl_mtx);
vcl->temp = VTAILQ_EMPTY(&vcl->ref_list) ?
VCL_TEMP_COLD : VCL_TEMP_COOLING;
vdire_start_event(vcl->vdire, VTAILQ_EMPTY(&vcl->ref_list) ?
VCL_TEMP_COLD : VCL_TEMP_COOLING);
Lck_Unlock(&vcl_mtx);
vcl_BackendEvent(vcl, VCL_EVENT_COLD);
backend_event_base(vcl, VCL_EVENT_COLD);
vdire_end_event(vcl->vdire);
// delta directors at VCL_TEMP_COLD do not need an event
AZ(vcl_send_event(vcl, VCL_EVENT_COLD, msg));
AZ(*msg);
}
Expand All @@ -769,16 +849,19 @@ vcl_set_state(struct vcl *vcl, const char *state, struct vsb **msg)
}
else {
Lck_Lock(&vcl_mtx);
vcl->temp = VCL_TEMP_WARM;
vdire_start_event(vcl->vdire, VCL_TEMP_WARM);
Lck_Unlock(&vcl_mtx);
i = vcl_send_event(vcl, VCL_EVENT_WARM, msg);
if (i == 0) {
vcl_BackendEvent(vcl, VCL_EVENT_WARM);
backend_event_base(vcl, VCL_EVENT_WARM);
// delta directors are already warm
vdire_end_event(vcl->vdire);
break;
}
AZ(vcl_send_event(vcl, VCL_EVENT_COLD, &nomsg));
AZ(nomsg);
vcl->temp = VCL_TEMP_COLD;
backend_event_delta(vcl, VCL_EVENT_COLD, VCL_TEMP_COLD);
vdire_end_event(vcl->vdire);
}
break;
default:
Expand Down
2 changes: 2 additions & 0 deletions bin/varnishd/cache/cache_vcl.h
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Original file line number Diff line number Diff line change
Expand Up @@ -50,6 +50,8 @@ struct vdire {
// to signal when iterators can enter again
pthread_cond_t cond;
const struct vcltemp **tempp;
// last director present when vdire_start_event is called
struct vcldir *checkpoint;
};

struct vcl {
Expand Down