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116 lines
3.9 KiB
116 lines
3.9 KiB
commit 31470e2ba2aabb4c6340fbc15cb5486ceb8c69c8
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Author: Olivier Houchard <ohouchard@haproxy.com>
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Date: Mon Apr 29 18:52:06 2019 +0200
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BUG/MEDIUM: port_range: Make the ring buffer lock-free.
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Port range uses a ring buffer, and unfortunately, when making haproxy
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multithreaded, it's been overlooked, and the ring buffer is not thread-safe.
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When specifying a source range, 2 or more threads could pick the same
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port, and of course only one of them could use the port, the others would
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always fail the connection.
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To fix this, make it a lock-free ring buffer. This is easier than usual
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because we know the ring buffer can never be full.
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This should be backported to 1.8 and 1.9.
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(cherry picked from commit 07425de71777b688e77a9c70a7088c13e66e41e9)
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Signed-off-by: Olivier Houchard <cognet@ci0.org>
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(cherry picked from commit bffb51147a4a5939e344b3c838628f9a944febef)
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Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>
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diff --git a/include/proto/port_range.h b/include/proto/port_range.h
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index 8c63faca..f7e3f1d5 100644
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--- a/include/proto/port_range.h
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+++ b/include/proto/port_range.h
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@@ -24,18 +24,22 @@
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#include <types/port_range.h>
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+#define GET_NEXT_OFF(range, off) ((off) == (range)->size - 1 ? 0 : (off) + 1)
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+
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/* return an available port from range <range>, or zero if none is left */
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static inline int port_range_alloc_port(struct port_range *range)
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{
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int ret;
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+ int get;
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+ int put;
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- if (!range->avail)
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- return 0;
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- ret = range->ports[range->get];
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- range->get++;
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- if (range->get >= range->size)
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- range->get = 0;
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- range->avail--;
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+ get = HA_ATOMIC_LOAD(&range->get);
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+ do {
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+ put = HA_ATOMIC_LOAD(&range->put_t);
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+ if (unlikely(put == get))
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+ return 0;
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+ ret = range->ports[get];
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+ } while (!(HA_ATOMIC_CAS(&range->get, &get, GET_NEXT_OFF(range, get))));
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return ret;
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}
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@@ -45,14 +49,28 @@ static inline int port_range_alloc_port(struct port_range *range)
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*/
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static inline void port_range_release_port(struct port_range *range, int port)
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{
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+ int put;
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+
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if (!port || !range)
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return;
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- range->ports[range->put] = port;
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- range->avail++;
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- range->put++;
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- if (range->put >= range->size)
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- range->put = 0;
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+ put = range->put_h;
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+ /* put_h is reserved for producers, so that they can each get a
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+ * free slot, put_t is what is used by consumers to know if there's
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+ * elements available or not
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+ */
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+ /* First reserve or slot, we know the ring buffer can't be full,
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+ * as we will only ever release port we allocated before
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+ */
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+ while (!(HA_ATOMIC_CAS(&range->put_h, &put, GET_NEXT_OFF(range, put))));
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+ HA_ATOMIC_STORE(&range->ports[put], port);
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+ /* Wait until all the threads that got a slot before us are done */
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+ while ((volatile int)range->put_t != put)
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+ __ha_compiler_barrier();
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+ /* Let the world know we're done, and any potential consumer they
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+ * can use that port.
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+ */
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+ HA_ATOMIC_STORE(&range->put_t, GET_NEXT_OFF(range, put));
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}
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/* return a new initialized port range of N ports. The ports are not
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@@ -62,8 +80,10 @@ static inline struct port_range *port_range_alloc_range(int n)
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{
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struct port_range *ret;
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ret = calloc(1, sizeof(struct port_range) +
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- n * sizeof(((struct port_range *)0)->ports[0]));
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- ret->size = ret->avail = n;
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+ (n + 1) * sizeof(((struct port_range *)0)->ports[0]));
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+ ret->size = n + 1;
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+ /* Start at the first free element */
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+ ret->put_h = ret->put_t = n;
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return ret;
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}
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diff --git a/include/types/port_range.h b/include/types/port_range.h
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index 1d010f77..33455d2d 100644
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--- a/include/types/port_range.h
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+++ b/include/types/port_range.h
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@@ -25,8 +25,7 @@
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#include <netinet/in.h>
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struct port_range {
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- int size, get, put; /* range size, and get/put positions */
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- int avail; /* number of available ports left */
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+ int size, get, put_h, put_t; /* range size, and get/put positions */
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uint16_t ports[0]; /* array of <size> ports, in host byte order */
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};
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