From: Eric Wong <e@80x24.org>
To: mwrap-public@80x24.org
Subject: [PATCH 03/19] hold RCU read lock to insert each allocation
Date: Mon, 16 Jul 2018 21:19:17 +0000 [thread overview]
Message-ID: <20180716211933.5835-4-e@80x24.org> (raw)
In-Reply-To: <20180716211933.5835-1-e@80x24.org>
We need to hold the RCU read lock to ensure the liveness
of the associated src_loc struct we'll be inserting into.
---
ext/mwrap/mwrap.c | 68 ++++++++++++++++++++++++++++++-----------------
1 file changed, 43 insertions(+), 25 deletions(-)
diff --git a/ext/mwrap/mwrap.c b/ext/mwrap/mwrap.c
index 0da7a68..8d8b19f 100644
--- a/ext/mwrap/mwrap.c
+++ b/ext/mwrap/mwrap.c
@@ -241,7 +241,7 @@ static int loc_eq(struct cds_lfht_node *node, const void *key)
memcmp(k->k, existing->k, loc_size(k)) == 0);
}
-static struct src_loc *totals_add(struct src_loc *k)
+static struct src_loc *totals_add_rcu(struct src_loc *k)
{
struct cds_lfht_iter iter;
struct cds_lfht_node *cur;
@@ -249,7 +249,6 @@ static struct src_loc *totals_add(struct src_loc *k)
struct cds_lfht *t;
again:
- rcu_read_lock();
t = rcu_dereference(totals);
if (!t) goto out_unlock;
cds_lfht_lookup(t, k->hval, loc_eq, k, &iter);
@@ -270,20 +269,22 @@ again:
if (cur != &l->hnode) { /* lost race */
rcu_read_unlock();
real_free(l);
+ rcu_read_lock();
goto again;
}
}
out_unlock:
- rcu_read_unlock();
return l;
}
-static struct src_loc *update_stats(size_t size, uintptr_t caller)
+static struct src_loc *update_stats_rcu(size_t size, uintptr_t caller)
{
struct src_loc *k, *ret = 0;
static const size_t xlen = sizeof(caller);
char *dst;
+ assert(rcu_read_ongoing());
+
if (locating++) goto out; /* do not recurse into another *alloc */
if (has_ec_p()) {
@@ -307,7 +308,7 @@ static struct src_loc *update_stats(size_t size, uintptr_t caller)
*dst = 0; /* terminate string */
k->capa = (uint32_t)(dst - k->k + 1);
k->hval = jhash(k->k, k->capa, 0xdeadbeef);
- ret = totals_add(k);
+ ret = totals_add_rcu(k);
} else {
rb_bug("bad math making key from location %s:%d\n",
ptr, line);
@@ -319,7 +320,7 @@ unknown:
memcpy(k->k, &caller, xlen);
k->capa = 0;
k->hval = jhash(k->k, xlen, 0xdeadbeef);
- ret = totals_add(k);
+ ret = totals_add_rcu(k);
}
out:
--locating;
@@ -356,8 +357,10 @@ void free(void *p)
}
static void
-alloc_insert(struct src_loc *l, struct alloc_hdr *h, size_t size, void *real)
+alloc_insert_rcu(struct src_loc *l, struct alloc_hdr *h, size_t size, void *real)
{
+ /* we need src_loc to remain alive for the duration of this call */
+ assert(rcu_read_ongoing());
if (!h) return;
h->size = size;
h->real = real;
@@ -403,13 +406,15 @@ static void *internal_memalign(size_t alignment, size_t size, uintptr_t caller)
return 0;
}
/* assert(asize == (alignment + size + sizeof(struct alloc_hdr))); */
- l = update_stats(size, caller);
+ rcu_read_lock();
+ l = update_stats_rcu(size, caller);
real = real_malloc(asize);
p = hdr2ptr(real);
if (!ptr_is_aligned(p, alignment))
p = ptr_align(p, alignment);
h = ptr2hdr(p);
- alloc_insert(l, h, size, real);
+ alloc_insert_rcu(l, h, size, real);
+ rcu_read_unlock();
return p;
}
@@ -468,17 +473,22 @@ void *malloc(size_t size)
struct src_loc *l;
struct alloc_hdr *h;
size_t asize;
+ void *p;
if (__builtin_add_overflow(size, sizeof(struct alloc_hdr), &asize)) {
errno = ENOMEM;
return 0;
}
RETURN_IF_NOT_READY();
- l = update_stats(size, RETURN_ADDRESS(0));
- h = real_malloc(asize);
- if (!h) return 0;
- alloc_insert(l, h, size, h);
- return hdr2ptr(h);
+ rcu_read_lock();
+ l = update_stats_rcu(size, RETURN_ADDRESS(0));
+ p = h = real_malloc(asize);
+ if (h) {
+ alloc_insert_rcu(l, h, size, h);
+ p = hdr2ptr(h);
+ }
+ rcu_read_unlock();
+ return p;
}
void *calloc(size_t nmemb, size_t size)
@@ -497,12 +507,15 @@ void *calloc(size_t nmemb, size_t size)
return 0;
}
RETURN_IF_NOT_READY();
- l = update_stats(size, RETURN_ADDRESS(0));
- h = real_malloc(asize);
- if (!h) return 0;
- alloc_insert(l, h, size, h);
- p = hdr2ptr(h);
- memset(p, 0, size);
+ rcu_read_lock();
+ l = update_stats_rcu(size, RETURN_ADDRESS(0));
+ p = h = real_malloc(asize);
+ if (p) {
+ alloc_insert_rcu(l, h, size, h);
+ p = hdr2ptr(h);
+ memset(p, 0, size);
+ }
+ rcu_read_unlock();
return p;
}
@@ -522,11 +535,16 @@ void *realloc(void *ptr, size_t size)
return 0;
}
RETURN_IF_NOT_READY();
- l = update_stats(size, RETURN_ADDRESS(0));
- h = real_malloc(asize);
- if (!h) return 0;
- alloc_insert(l, h, size, h);
- p = hdr2ptr(h);
+
+ rcu_read_lock();
+ l = update_stats_rcu(size, RETURN_ADDRESS(0));
+ p = h = real_malloc(asize);
+ if (p) {
+ alloc_insert_rcu(l, h, size, h);
+ p = hdr2ptr(h);
+ }
+ rcu_read_unlock();
+
if (ptr) {
struct alloc_hdr *old = ptr2hdr(ptr);
memcpy(p, ptr, old->size < size ? old->size : size);
--
EW
next prev parent reply other threads:[~2018-07-16 21:19 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-07-16 21:19 [PATCH 0/19] the heavy version of mwrap Eric Wong
2018-07-16 21:19 ` [PATCH 01/19] support per-allocation headers for per-alloc tracking Eric Wong
2018-07-16 21:19 ` [PATCH 02/19] mwrap: use malloc to do our own memalign Eric Wong
2018-07-16 21:19 ` Eric Wong [this message]
2018-07-16 21:19 ` [PATCH 04/19] realloc: do not copy if allocation failed Eric Wong
2018-07-16 21:19 ` [PATCH 05/19] internal_memalign: do not assume real_malloc succeeds Eric Wong
2018-07-16 21:19 ` [PATCH 06/19] ensure ENOMEM is preserved in errno when appropriate Eric Wong
2018-07-16 21:19 ` [PATCH 07/19] memalign: check alignment on all public functions Eric Wong
2018-07-16 21:19 ` [PATCH 08/19] reduce stack usage from file names Eric Wong
2018-07-16 21:19 ` [PATCH 09/19] resolve real_malloc earlier for C++ programs Eric Wong
2018-07-16 21:19 ` [PATCH 10/19] allow analyzing live allocations via Mwrap[location] Eric Wong
2018-07-16 21:19 ` [PATCH 11/19] alias Mwrap.clear to Mwrap.reset Eric Wong
2018-07-16 21:19 ` [PATCH 12/19] implement accessors for SourceLocation Eric Wong
2018-07-16 21:19 ` [PATCH 13/19] mwrap_aref: quiet -Wshorten-64-to-32 warning Eric Wong
2018-07-16 21:19 ` [PATCH 14/19] fixes for FreeBSD 11.1 Eric Wong
2018-07-16 21:19 ` [PATCH 15/19] use memrchr to extract address under glibc Eric Wong
2018-07-16 21:19 ` [PATCH 16/19] do not track allocations for constructor and Init_ Eric Wong
2018-07-16 21:19 ` [PATCH 17/19] disable memalign tracking by default Eric Wong
2018-07-16 21:19 ` [PATCH 18/19] support Mwrap.quiet to temporarily disable allocation tracking Eric Wong
2018-07-16 21:19 ` [PATCH 19/19] mwrap_rack: Rack app to track live allocations Eric Wong
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