Re: [alsa-devel] [PATCH] conf: don't check if config files are up to date

On Sun, 01 May 2016 14:43:42 +0200, Alexander E. Patrakov wrote:

Even if no files have been changed, the config may become outdated due to hot-plugged devices.

Note: this patch has a huge potential to crash badly-written applications that keep config pointers and strings for too long. But I see no other way to support hot-pluggable devices.

Can we opt in this feature, e.g. by enabling it via some new API function? Enabling this blindly appears too risky.

thanks,

Takashi

Fixes: https://bugs.freedesktop.org/show_bug.cgi?id=54029 Signed-off-by: Alexander E. Patrakov patrakov@gmail.com

---

src/conf.c | 63 ++++++++++++++++++++++++---------------------------------- src/confmisc.c | 4 +++- 2 files changed, 29 insertions(+), 38 deletions(-)

diff --git a/src/conf.c b/src/conf.c index f8b7a66..34576aa 100644 --- a/src/conf.c +++ b/src/conf.c @@ -3661,14 +3661,15 @@ SND_DLSYM_BUILD_VERSION(snd_config_hook_load_for_all_cards, SND_CONFIG_DLSYM_VER #endif

/**

• • \brief Updates a configuration tree by rereading the configuration files (if needed).

• • \brief Updates a configuration tree by rereading the configuration files.
  • \param[in,out] _top Address of the handle to the top-level node.
  • \param[in,out] _update Address of a pointer to private update information.
  • \param[in] cfgs A list of configuration file names, delimited with ':'.

  •             If \p cfgs is \c NULL, the default global
    

  •             configuration file is used.
    

• • \return 0 if \a _top was up to date, 1 if the configuration files

• •     have been reread, otherwise a negative error code.
    

• • \return 0 if \a _top was up to date (this can happen only in previous

• •             ALSA-lib versions), 1 if the configuration files have been
    

• •             reread successfully, otherwise a negative error code.
    

  • The variables pointed to by \a _top and \a _update can be initialized
  • to \c NULL before the first call to this function. The private

@@ -3679,7 +3680,8 @@ SND_DLSYM_BUILD_VERSION(snd_config_hook_load_for_all_cards, SND_CONFIG_DLSYM_VER

• The global configuration files are specified in the environment variable
• \c ALSA_CONFIG_PATH.

• • \warning If the configuration tree is reread, all string pointers and

• • \warning In order to deal with hot-pluggable devices, the configuration
• • tree is always reread, even if nothing changed. All string pointers and
  • configuration node handles previously obtained from this tree become
  • invalid.

@@ -3754,35 +3756,6 @@ int snd_config_update_r(snd_config_t **_top, snd_config_update_t **_update, cons local->count--; } }

• if (!update)

• goto _reread;
  

• if (local->count != update->count)

• goto _reread;
  

• for (k = 0; k < local->count; ++k) {

• struct finfo *lf = &local->finfo[k];
  

• struct finfo *uf = &update->finfo[k];
  

• if (strcmp(lf->name, uf->name) != 0 ||
  

•     lf->dev != uf->dev ||
  

•     lf->ino != uf->ino ||
  

•     lf->mtime != uf->mtime)
  

• 	goto _reread;
  

• }

• err = 0;

• _end:

• if (err < 0) {

• if (top) {
  

• 	snd_config_delete(top);
  

• 	*_top = NULL;
  

• }
  

• if (update) {
  

• 	snd_config_update_free(update);
  

• 	*_update = NULL;
  

• }
  

• }

• if (local)

• snd_config_update_free(local);
  

• return err;

  _reread: *_top = NULL;

@@ -3823,15 +3796,31 @@ int snd_config_update_r(snd_config_t **_top, snd_config_update_t **_update, cons *_top = top; *_update = local; return 1;

+_end:

• if (err < 0) {

• if (top) {
  

• 	snd_config_delete(top);
  

• 	*_top = NULL;
  

• }
  

• if (update) {
  

• 	snd_config_update_free(update);
  

• 	*_update = NULL;
  

• }
  

• }
• if (local)

• snd_config_update_free(local);
  

• return err;

}

/**

• • \brief Updates #snd_config by rereading the global configuration files (if needed).
• • \return 0 if #snd_config was up to date, 1 if #snd_config was

• •     updated, otherwise a negative error code.
    

• • \brief Updates #snd_config by rereading the global configuration files.
• • \return 0 if #snd_config was up to date (this can happen only in previous

• •     ALSA-lib versions), 1 if #snd_config was updated successfully,
    

• •     otherwise a negative error code.
    

  • \warning Whenever #snd_config is updated, all string pointers and

• • configuration node handles previously obtained from it may become

• • configuration node handles previously obtained from it become
  • invalid.
  • \par Errors:

diff --git a/src/confmisc.c b/src/confmisc.c index ae0275f..8f97b72 100644 --- a/src/confmisc.c +++ b/src/confmisc.c @@ -599,7 +599,9 @@ static int open_ctl(long card, snd_ctl_t **ctl) char name[16]; snprintf(name, sizeof(name), "hw:%li", card); name[sizeof(name)-1] = '\0';

• return snd_ctl_open(ctl, name, 0);

• /* Take care not to update the config - we may be running hooks on pcms right now */
• return snd_ctl_open_lconf(ctl, name, 0, snd_config);

}

#if 0

2.8.0