d/freebsd-skq
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

ktrace_resize_pool() locking slightly reworked:

Browse Source 
1) do not take a lock around the single atomic operation.
2) do not lose the invariant of lock by dropping/acquiring
   ktrace_mtx around free() or malloc().

MFC after:	1 Month.
This commit is contained in:
Dmitry Chagin 2011-02-25 22:03:28 +00:00
parent 2960733f48
commit b4c20e5e37
1 changed files with 16 additions and 18 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

34
sys/kern/kern_ktrace.c
View File

@ -133,7 +133,7 @@ static struct sx ktrace_sx;
static void ktrace_init(void *dummy); static void ktrace_init(void *dummy);
static int sysctl_kern_ktrace_request_pool(SYSCTL_HANDLER_ARGS); static int sysctl_kern_ktrace_request_pool(SYSCTL_HANDLER_ARGS);
static u_int ktrace_resize_pool(u_int newsize); static u_int ktrace_resize_pool(u_int oldsize, u_int newsize);
static struct ktr_request *ktr_getrequest(int type); static struct ktr_request *ktr_getrequest(int type);
static void ktr_submitrequest(struct thread *td, struct ktr_request *req); static void ktr_submitrequest(struct thread *td, struct ktr_request *req);
static void ktr_freeproc(struct proc *p, struct ucred **uc, static void ktr_freeproc(struct proc *p, struct ucred **uc,
@ -199,9 +199,7 @@ sysctl_kern_ktrace_request_pool(SYSCTL_HANDLER_ARGS)
/* Handle easy read-only case first to avoid warnings from GCC. */ /* Handle easy read-only case first to avoid warnings from GCC. */
if (!req->newptr) { if (!req->newptr) {
mtx_lock(&ktrace_mtx);
oldsize = ktr_requestpool; oldsize = ktr_requestpool;
mtx_unlock(&ktrace_mtx);
return (SYSCTL_OUT(req, &oldsize, sizeof(u_int))); return (SYSCTL_OUT(req, &oldsize, sizeof(u_int)));
} }
@ -210,10 +208,8 @@ sysctl_kern_ktrace_request_pool(SYSCTL_HANDLER_ARGS)
return (error); return (error);
td = curthread; td = curthread;
ktrace_enter(td); ktrace_enter(td);
mtx_lock(&ktrace_mtx);
oldsize = ktr_requestpool; oldsize = ktr_requestpool;
newsize = ktrace_resize_pool(wantsize); newsize = ktrace_resize_pool(oldsize, wantsize);
mtx_unlock(&ktrace_mtx);
ktrace_exit(td); ktrace_exit(td);
error = SYSCTL_OUT(req, &oldsize, sizeof(u_int)); error = SYSCTL_OUT(req, &oldsize, sizeof(u_int));
if (error) if (error)
@ -227,38 +223,40 @@ SYSCTL_PROC(_kern_ktrace, OID_AUTO, request_pool, CTLTYPE_UINT|CTLFLAG_RW,
"Pool buffer size for ktrace(1)"); "Pool buffer size for ktrace(1)");
static u_int static u_int
ktrace_resize_pool(u_int newsize) ktrace_resize_pool(u_int oldsize, u_int newsize)
{ {
STAILQ_HEAD(, ktr_request) ktr_new;
struct ktr_request *req; struct ktr_request *req;
int bound; int bound;
mtx_assert(&ktrace_mtx, MA_OWNED);
print_message = 1; print_message = 1;
bound = newsize - ktr_requestpool; bound = newsize - oldsize;
if (bound == 0) if (bound == 0)
return (ktr_requestpool); return (ktr_requestpool);
if (bound < 0) if (bound < 0) {
mtx_lock(&ktrace_mtx);
/* Shrink pool down to newsize if possible. */ /* Shrink pool down to newsize if possible. */
while (bound++ < 0) { while (bound++ < 0) {
req = STAILQ_FIRST(&ktr_free); req = STAILQ_FIRST(&ktr_free);
if (req == NULL) if (req == NULL)
return (ktr_requestpool); break;
STAILQ_REMOVE_HEAD(&ktr_free, ktr_list); STAILQ_REMOVE_HEAD(&ktr_free, ktr_list);
ktr_requestpool--; ktr_requestpool--;
mtx_unlock(&ktrace_mtx);
free(req, M_KTRACE); free(req, M_KTRACE);
mtx_lock(&ktrace_mtx);
} }
else } else {
/* Grow pool up to newsize. */ /* Grow pool up to newsize. */
STAILQ_INIT(&ktr_new);
while (bound-- > 0) { while (bound-- > 0) {
mtx_unlock(&ktrace_mtx);
req = malloc(sizeof(struct ktr_request), M_KTRACE, req = malloc(sizeof(struct ktr_request), M_KTRACE,
M_WAITOK); M_WAITOK);
mtx_lock(&ktrace_mtx); STAILQ_INSERT_HEAD(&ktr_new, req, ktr_list);
STAILQ_INSERT_HEAD(&ktr_free, req, ktr_list);
ktr_requestpool++;
} }
mtx_lock(&ktrace_mtx);
STAILQ_CONCAT(&ktr_free, &ktr_new);
ktr_requestpool += (newsize - oldsize);
}
mtx_unlock(&ktrace_mtx);
return (ktr_requestpool); return (ktr_requestpool);
} }