[pulseaudio-discuss] [PATCH v2 02/12] pulsecore: srbchannel: Introduce per-client SHM files
David Henningsson
david.henningsson at canonical.com
Fri Feb 12 13:55:32 UTC 2016
On 2016-02-12 01:09, Ahmed S. Darwish wrote:
> The PA daemon currently uses a single SHM file for all the clients
> sending and receiving commands over the low-latency srbchannel
> mechanism.
>
> To safely run PA daemon in system mode later using memfds, and to
> provide the necessary ground work for sandboxing, create the
> srbchannel SHM files on a per-client basis.
>
> Signed-off-by: Ahmed S. Darwish <darwish.07 at gmail.com>
> ---
> src/pulsecore/core.c | 19 ++++++++++---------
> src/pulsecore/core.h | 6 ++----
> src/pulsecore/protocol-native.c | 28 ++++++++++++++++++++++++----
> 3 files changed, 36 insertions(+), 17 deletions(-)
>
> [ For more details on the vacuuming issue, please check the
> message sent in direct reply to this patch.. ]
If the srbchannel is the only thing present in that pool, then vacuuming
does not even make sense?
>
> diff --git a/src/pulsecore/core.c b/src/pulsecore/core.c
> index b2df7de..1c3c3cd 100644
> --- a/src/pulsecore/core.c
> +++ b/src/pulsecore/core.c
> @@ -126,11 +126,6 @@ pa_core* pa_core_new(pa_mainloop_api *m, bool shared, size_t shm_size) {
> c->shm_size = shm_size;
> pa_silence_cache_init(&c->silence_cache);
>
> - if (shared && !(c->rw_mempool = pa_mempool_new(shared, shm_size)))
> - pa_log_warn("Failed to allocate shared writable memory pool.");
> - if (c->rw_mempool)
> - pa_mempool_set_is_remote_writable(c->rw_mempool, true);
> -
> c->exit_event = NULL;
> c->scache_auto_unload_event = NULL;
>
> @@ -217,8 +212,6 @@ static void core_free(pa_object *o) {
> pa_assert(!c->default_sink);
>
> pa_silence_cache_done(&c->silence_cache);
> - if (c->rw_mempool)
> - pa_mempool_free(c->rw_mempool);
> pa_mempool_free(c->mempool);
>
> for (j = 0; j < PA_CORE_HOOK_MAX; j++)
> @@ -285,8 +278,16 @@ void pa_core_maybe_vacuum(pa_core *c) {
>
> pa_mempool_vacuum(c->mempool);
>
> - if (c->rw_mempool)
> - pa_mempool_vacuum(c->rw_mempool);
> + /*
> + * FIXME: Vacuum the per-client rw (srbchannel) mempools
> + *
> + * We need to vacuum the per-client mempool owned by each connection
> + * at pa_native_protocol::connections. Nonetheless, libpulsecore can
> + * not access any symbol from protocol-native.
> + *
> + * Vacuuming a per-client mempool on its streams deletion and
> + * uncorking also proved to be problematic.
> + */
> }
>
> pa_time_event* pa_core_rttime_new(pa_core *c, pa_usec_t usec, pa_time_event_cb_t cb, void *userdata) {
> diff --git a/src/pulsecore/core.h b/src/pulsecore/core.h
> index 428689c..9f5c445 100644
> --- a/src/pulsecore/core.h
> +++ b/src/pulsecore/core.h
> @@ -177,10 +177,8 @@ struct pa_core {
> PA_LLIST_HEAD(pa_subscription_event, subscription_event_queue);
> pa_subscription_event *subscription_event_last;
>
> - /* The mempool is used for data we write to, it's readonly for the client.
> - The rw_mempool is used for data writable by both server and client (and
> - can be NULL in some cases). */
> - pa_mempool *mempool, *rw_mempool;
> + /* The mempool is used for data we write to, it's readonly for the client. */
> + pa_mempool *mempool;
>
> /* Shared memory size, as specified either by daemon configuration
> * or PA daemon defaults (~ 64 MiB). */
> diff --git a/src/pulsecore/protocol-native.c b/src/pulsecore/protocol-native.c
> index 145db04..c6b3ca4 100644
> --- a/src/pulsecore/protocol-native.c
> +++ b/src/pulsecore/protocol-native.c
> @@ -173,6 +173,12 @@ struct pa_native_connection {
> bool is_local:1;
> uint32_t version;
> pa_client *client;
> + /* R/W mempool, one per client connection, for srbchannel transport.
> + * Both server and client can write to this shm area.
> + *
> + * Note: This will be NULL if our connection with the client does
> + * not support srbchannels */
> + pa_mempool *rw_mempool;
> pa_pstream *pstream;
> pa_pdispatch *pdispatch;
> pa_idxset *record_streams, *output_streams;
> @@ -1348,6 +1354,12 @@ static void native_connection_unlink(pa_native_connection *c) {
> if (c->pstream)
> pa_pstream_unlink(c->pstream);
>
> + /* This mempool is used exclusively by srbchanels. Do not free it
> + * except after ending all srbchannel communications through the
> + * pstreams unlink above */
> + if (c->rw_mempool)
> + pa_mempool_free(c->rw_mempool);
A general convention for _unlink functions is that they should allow
being called more than one time. So all places which free the mempool
should also set the variable to NULL.
> +
> if (c->auth_timeout_event) {
> c->protocol->core->mainloop->time_free(c->auth_timeout_event);
> c->auth_timeout_event = NULL;
> @@ -2606,15 +2618,17 @@ static void setup_srbchannel(pa_native_connection *c) {
> return;
> }
>
> - if (!c->protocol->core->rw_mempool) {
> - pa_log_debug("Disabling srbchannel, reason: No rw memory pool");
What if c->rw_mempool is already set at this point? Can that happen? If
not, add an assertion, if it can (consider a malicious client) ...then
handle it somehow :-)
> + if (!(c->rw_mempool = pa_mempool_new(true, c->protocol->core->shm_size))) {
> + pa_log_warn("Disabling srbchannel, reason: Failed to allocate shared "
> + "writable memory pool.");
> return;
> }
> + pa_mempool_set_is_remote_writable(c->rw_mempool, true);
>
> - srb = pa_srbchannel_new(c->protocol->core->mainloop, c->protocol->core->rw_mempool);
> + srb = pa_srbchannel_new(c->protocol->core->mainloop, c->rw_mempool);
> if (!srb) {
> pa_log_debug("Failed to create srbchannel");
> - return;
> + goto free_rw_mempool;
If this is the only place you need goto, just instead do
pa_mempool_free(c->rw_mempool);
c->rw_mempool = NULL;
return;
> }
> pa_log_debug("Enabling srbchannel...");
> pa_srbchannel_export(srb, &srbt);
> @@ -2634,6 +2648,10 @@ static void setup_srbchannel(pa_native_connection *c) {
> pa_pstream_send_memblock(c->pstream, 0, 0, 0, &mc);
>
> c->srbpending = srb;
> + return;
> +
> +free_rw_mempool:
> + pa_mempool_free(c->rw_mempool);
> }
>
> static void command_enable_srbchannel(pa_pdispatch *pd, uint32_t command, uint32_t tag, pa_tagstruct *t, void *userdata) {
> @@ -5125,6 +5143,8 @@ void pa_native_protocol_connect(pa_native_protocol *p, pa_iochannel *io, pa_nati
> c->client->send_event = client_send_event_cb;
> c->client->userdata = c;
>
> + c->rw_mempool = NULL;
A preferred way nowadays is to instead use pa_xnew0 when creating the
struct initially.
> +
> c->pstream = pa_pstream_new(p->core->mainloop, io, p->core->mempool);
> pa_pstream_set_receive_packet_callback(c->pstream, pstream_packet_callback, c);
> pa_pstream_set_receive_memblock_callback(c->pstream, pstream_memblock_callback, c);
>
>
> Regards,
>
--
David Henningsson, Canonical Ltd.
https://launchpad.net/~diwic
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