[pulseaudio-discuss] [PATCH v2 08/12] pulsecore: Specially mark global mempools
Ahmed S. Darwish
darwish.07 at gmail.com
Fri Feb 12 00:18:00 UTC 2016
Color global mempools with a special mark. Almost all pools are
now created on a per client basis except the pa_core's mempool,
which is shared between all clients.
This special marking is needed for handling memfd-backed pools.
To avoid fd leaks, memfd pools are registered with the connection
pstream to create an ID<->memfd mapping on both PA endpoints.
Such memory regions are then always referenced by their IDs and
never by their fds, and so their fds can be safely closed later.
Unfortunately this scheme cannot work with global pools since the
registration ID<->memfd mechanism needs to happen for each newly
connected client, and thus the need for a more special handling.
Signed-off-by: Ahmed S. Darwish <darwish.07 at gmail.com>
---
src/pulsecore/core.c | 4 +--
src/pulsecore/memblock.c | 70 +++++++++++++++++++++++++++++++++++++++++++++++-
src/pulsecore/memblock.h | 3 +++
src/pulsecore/shm.h | 6 ++++-
4 files changed, 79 insertions(+), 4 deletions(-)
diff --git a/src/pulsecore/core.c b/src/pulsecore/core.c
index 4714932..aab82f3 100644
--- a/src/pulsecore/core.c
+++ b/src/pulsecore/core.c
@@ -69,14 +69,14 @@ pa_core* pa_core_new(pa_mainloop_api *m, bool shared, size_t shm_size) {
pa_assert(m);
if (shared) {
- if (!(pool = pa_mempool_new(PA_MEM_TYPE_SHARED_POSIX, shm_size))) {
+ if (!(pool = pa_global_mempool_new(PA_MEM_TYPE_SHARED_POSIX, shm_size))) {
pa_log_warn("Failed to allocate shared memory pool. Falling back to a normal memory pool.");
shared = false;
}
}
if (!shared) {
- if (!(pool = pa_mempool_new(PA_MEM_TYPE_PRIVATE, shm_size))) {
+ if (!(pool = pa_global_mempool_new(PA_MEM_TYPE_PRIVATE, shm_size))) {
pa_log("pa_mempool_new() failed.");
return NULL;
}
diff --git a/src/pulsecore/memblock.c b/src/pulsecore/memblock.c
index af27ba5..9c31e53 100644
--- a/src/pulsecore/memblock.c
+++ b/src/pulsecore/memblock.c
@@ -169,6 +169,29 @@ struct pa_mempool {
} per_type;
};
+ /* Color global mempools with a special mark.
+ *
+ * Mempools are now created on a per client basis by default. The
+ * only exception is the pa_core's mempool, which is shared between
+ * all clients of the system.
+ *
+ * This special mark is needed for handling memfd pools.
+ *
+ * To avoid fd leaks, memfd pools are registered with the connection
+ * pstream to create an ID<->memfd mapping on both PA endpoints.
+ * Such memory regions are then always referenced by their IDs and
+ * never by their fds, and so their fds can be safely closed later.
+ *
+ * Unfortunately this scheme cannot work with global pools since the
+ * registration ID<->memfd mechanism needs to happen for each newly
+ * connected client, and thus the need for a more special handling.
+ *
+ * TODO: Transform the core mempool into a per-client one and remove
+ * global pools support. They conflict with the futuristic xdg-app
+ * model and complicates handling of memfd-based pools.
+ */
+ bool global;
+
size_t block_size;
unsigned n_blocks;
bool is_remote_writable;
@@ -767,7 +790,7 @@ static void memblock_replace_import(pa_memblock *b) {
pa_mutex_unlock(import->mutex);
}
-pa_mempool *pa_mempool_new(pa_mem_type_t type, size_t size) {
+static pa_mempool *mempool_new(pa_mem_type_t type, size_t size, bool global) {
pa_mempool *p;
char t1[PA_BYTES_SNPRINT_MAX], t2[PA_BYTES_SNPRINT_MAX];
@@ -802,6 +825,8 @@ pa_mempool *pa_mempool_new(pa_mem_type_t type, size_t size) {
pa_bytes_snprint(t2, sizeof(t2), (unsigned) (p->n_blocks * p->block_size)),
(unsigned long) pa_mempool_block_size_max(p));
+ p->global = global;
+
pa_atomic_store(&p->n_init, 0);
PA_LLIST_HEAD_INIT(pa_memimport, p->imports);
@@ -819,6 +844,15 @@ mem_create_fail:
return NULL;
}
+pa_mempool *pa_mempool_new(pa_mem_type_t type, size_t size) {
+ return mempool_new(type, size, false);
+}
+
+/* Check comments on top of pa_mempool.global for details */
+pa_mempool *pa_global_mempool_new(pa_mem_type_t type, size_t size) {
+ return mempool_new(type, size, true);
+}
+
void pa_mempool_free(pa_mempool *p) {
pa_assert(p);
@@ -953,6 +987,18 @@ bool pa_mempool_is_memfd_backed(const pa_mempool *p) {
(p->per_type.shm.type == PA_MEM_TYPE_SHARED_MEMFD);
}
+/* No lock necessary */
+bool pa_mempool_is_global(pa_mempool *p) {
+ pa_assert(p);
+
+ return p->global;
+}
+
+/* No lock necessary */
+static bool pa_mempool_is_per_client(pa_mempool *p) {
+ return !pa_mempool_is_global(p);
+}
+
/* Self-locked
*
* Check the comments over pa_shm->per_type.memfd.fd for context.
@@ -964,6 +1010,8 @@ int pa_mempool_get_and_reset_shm_memfd_fd(pa_mempool *p) {
pa_shm *memory;
int memfd_fd;
+ pa_assert(p);
+ pa_assert(pa_mempool_is_per_client(p));
pa_assert(pa_mempool_is_shared(p));
pa_assert(pa_mempool_is_memfd_backed(p));
@@ -979,6 +1027,26 @@ int pa_mempool_get_and_reset_shm_memfd_fd(pa_mempool *p) {
return memfd_fd;
}
+/* No lock necessary
+ *
+ * Global mempools have their memfd descriptor always open. DO NOT
+ * close the returned descriptor by your own!
+ *
+ * Check pa_mempool.global for further context. */
+int pa_global_mempool_get_shm_memfd_fd(pa_mempool *p) {
+ int memfd_fd;
+
+ pa_assert(p);
+ pa_assert(pa_mempool_is_shared(p));
+ pa_assert(pa_mempool_is_memfd_backed(p));
+ pa_assert(pa_mempool_is_global(p));
+
+ memfd_fd = p->per_type.shm.per_type.memfd.fd;
+ pa_assert(memfd_fd != -1);
+
+ return memfd_fd;
+}
+
/* For receiving blocks from other nodes */
pa_memimport* pa_memimport_new(pa_mempool *p, pa_memimport_release_cb_t cb, void *userdata) {
pa_memimport *i;
diff --git a/src/pulsecore/memblock.h b/src/pulsecore/memblock.h
index 059538f..b2f5e31 100644
--- a/src/pulsecore/memblock.h
+++ b/src/pulsecore/memblock.h
@@ -123,17 +123,20 @@ pa_memblock *pa_memblock_will_need(pa_memblock *b);
/* The memory block manager */
pa_mempool *pa_mempool_new(pa_mem_type_t type, size_t size);
+pa_mempool *pa_global_mempool_new(pa_mem_type_t type, size_t size);
void pa_mempool_free(pa_mempool *p);
const pa_mempool_stat* pa_mempool_get_stat(pa_mempool *p);
void pa_mempool_vacuum(pa_mempool *p);
int pa_mempool_get_shm_id(pa_mempool *p, uint32_t *id);
bool pa_mempool_is_shared(const pa_mempool *p);
bool pa_mempool_is_memfd_backed(const pa_mempool *p);
+bool pa_mempool_is_global(pa_mempool *p);
bool pa_mempool_is_remote_writable(pa_mempool *p);
void pa_mempool_set_is_remote_writable(pa_mempool *p, bool writable);
size_t pa_mempool_block_size_max(pa_mempool *p);
int pa_mempool_get_and_reset_shm_memfd_fd(pa_mempool *p);
+int pa_global_mempool_get_shm_memfd_fd(pa_mempool *p);
/* For receiving blocks from other nodes */
pa_memimport* pa_memimport_new(pa_mempool *p, pa_memimport_release_cb_t cb, void *userdata);
diff --git a/src/pulsecore/shm.h b/src/pulsecore/shm.h
index e83a36c..f6b9d89 100644
--- a/src/pulsecore/shm.h
+++ b/src/pulsecore/shm.h
@@ -43,7 +43,11 @@ typedef struct pa_shm {
*
* When we don't have ownership for the memfd fd in question (e.g.
* memfd segment attachment), or the file descriptor has now been
- * closed, this is set to -1. */
+ * closed, this is set to -1.
+ *
+ * For the special case of a global mempool, we keep this fd
+ * always open. Check comments on top of pa_mempool.global for
+ * rationale. */
int fd;
} memfd;
} per_type;
Regards,
--
Darwish
http://darwish.chasingpointers.com
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