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hjfs: fix deadlocks

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buffers which still have requests queued on them are not free!

we cannot chanedev() a buffer while it has still requests queued on it
and we canot just queue our request (having different address) on the
buffer while there are other requests before it, otherwise we would
create artificial block dependency that can cause deadlock.
This commit is contained in:
cinap_lenrek 2015-08-13 10:41:12 +02:00
parent 8c4bb53bdc
commit 592b8d5b35
1 changed files with 39 additions and 36 deletions
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75
sys/src/cmd/hjfs/buf.c
View file

@ -54,14 +54,26 @@ delayreq(BufReq req, BufReq **first, BufReq **last)
BufReq *r;
r = emalloc(sizeof(*r));
memcpy(r, &req, sizeof(*r));
*r = req;
r->next = nil;
if(*first == nil)
*first = *last = r;
else{
*first = r;
else
(*last)->next = r;
*last = r;
}
*last = r;
}
static BufReq
undelayreq(BufReq **first, BufReq **last)
{
BufReq r;
r = **first;
free(*first);
*first = r.next;
if(r.next == nil)
*last = nil;
return r;
}
static void
@ -81,7 +93,7 @@ givebuf(BufReq req, Buf *b)
{
Buf *c, *l;
assert(!b->busy);
again:
if(req.d == b->d && req.off == b->off){
markbusy(b);
send(req.resp, &b);
@ -90,19 +102,30 @@ givebuf(BufReq req, Buf *b)
l = &req.d->buf[req.off & BUFHASH];
for(c = l->dnext; c != l; c = c->dnext)
if(c->off == req.off){
if(c->busy){
if(c->busy)
delayreq(req, &c->next, &c->last);
return;
else{
markbusy(c);
send(req.resp, &c);
}
markbusy(c);
send(req.resp, &c);
return;
if(b->next == nil)
return;
req = undelayreq(&b->next, &b->last);
goto again;
}
if(b->next != nil){
givebuf(undelayreq(&b->next, &b->last), b);
b = bfree.fnext;
}
if(b == &bfree){
delayreq(req, &freereq, &freereqlast);
return;
}
markbusy(b);
if(b->op & BDELWRI){
if(b->d != nil && b->op & BDELWRI){
delayreq(req, &b->next, &b->last);
b->op &= ~BDELWRI;
b->op |= BWRITE;
delayreq(req, &b->next, &b->last);
b->resp = putb;
work(b->d, b);
return;
@ -120,27 +143,7 @@ givebuf(BufReq req, Buf *b)
static void
handleget(BufReq req)
{
Buf *b;
b = bfree.fnext;
if(b == &bfree){
delayreq(req, &freereq, &freereqlast);
return;
}
givebuf(req, b);
}
static void
undelayreq(Buf *b, BufReq **first, BufReq **last)
{
BufReq *r;
r = *first;
*first = r->next;
if(*last == r)
*last = nil;
givebuf(*r, b);
free(r);
givebuf(req, bfree.fnext);
}
static void
@ -161,9 +164,9 @@ handleput(Buf *b)
b->op &= ~BWRITE;
markfree(b);
if(b->next != nil)
undelayreq(b, &b->next, &b->last);
givebuf(undelayreq(&b->next, &b->last), b);
else if(freereq != nil)
undelayreq(b, &freereq, &freereqlast);
givebuf(undelayreq(&freereq, &freereqlast), b);
}
static void