Currently, kernel/module annotates module dependencies when request_symbol is used, but it doesn't cover more complex inter-driver dependencies that are subsystem and/or driver-specific.
In the case of hdmi sound, depending on the CPU/GPU, sometimes the snd_hda_driver can talk directly with the hardware, but sometimes, it uses the i915 driver. When the snd_hda_driver uses i915, it should first be unbind/rmmod, as otherwise trying to unbind/rmmod the i915 driver cause driver issues, as as reported by CI tools with different GPU models: https://intel-gfx-ci.01.org/tree/drm-tip/IGT_6415/fi-tgl-1115g4/igt@core_hot... https://intel-gfx-ci.01.org/tree/drm-tip/CI_DRM_11495/bat-adlm-1/igt@i915_mo...
In the past, just a few CPUs were doing such bindings, but this issue now applies to all "modern" Intel CPUs that have onboard graphics, as well as to the newer discrete GPUs.
With the discrete GPU case, the HDA controller is physically separate and requires i915 to power on the hardware for all hardware access. In this case, the issue is hit basicly 100% of the time.
With on-board graphics, i915 driver is needed only when the display codec is accessed. If i915 is unbind during runtime suspend, while snd-hda-intel is still bound, nothing bad happens, but unbinding i915 on other situations may also cause issues.
So, add support at kernel/modules to allow snd-hda drivers to properly annotate when a dependency on a DRM driver dependencies exists, and add a call to such new function at the snd-hda driver when it successfully binds into the DRM driver.
This would allow userspace tools to check and properly remove the audio driver before trying to remove or unbind the GPU driver.
It should be noticed that this series conveys the hidden module dependencies. Other changes are needed in order to allow removing or unbinding the i915 driver while keeping the snd-hda-intel driver loaded/bound. With that regards, there are some discussions on how to improve this at alsa-devel a while back:
https://mailman.alsa-project.org/pipermail/alsa-devel/2021-September/190099....
So, future improvements on both in i915 and the audio drivers could be made. E.g. with discrete GPUs, it's the only codec of the card, so it seems feasible to detach the ALSA card if i915 is bound (using infra made for VGA switcheroo), but, until these improvements are done and land in upstream, audio drivers needs to be unbound if i915 driver goes unbind.
Yet, even if such fixes got merged, this series is still needed, as it makes such dependencies more explicit and easier to debug.
PS.: This series was generated against next-20220428.
---
v5: - while v4 works fine, it ends calling try_module_format() recursively, which is not what it it was supposed to do. So, change the logic to avoid such recursion, by adding a static __try_module_format() and renaming the new version that takes two arguments as try_module_format_owner().
v4: - fix a compilation warning reported by Intel's Kernel robot when !CONFIG_MODULE_UNLOAD or !CONFIG_MODULE.
v3: minor fixes: - fixed a checkpatch warning; - use a single line for the new function prototype.
v2: - the dependencies are now handled directly at try_module_get().
Mauro Carvalho Chehab (2): module: update dependencies at try_module_get() ALSA: hda - identify when audio is provided by a video driver
include/linux/module.h | 8 +++-- kernel/module/main.c | 65 ++++++++++++++++++++++++++++++-------- sound/hda/hdac_component.c | 2 +- 3 files changed, 57 insertions(+), 18 deletions(-)
Sometimes, device drivers are bound into each other via try_module_get(), making such references invisible when looking at /proc/modules or lsmod.
Add a function to allow setting up module references for such cases, and call it when try_module_get() is used.
Reviewed-by: Dan Williams dan.j.williams@intel.com Reviewed-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Mauro Carvalho Chehab mchehab@kernel.org ---
See [PATCH v5 0/2] at: https://lore.kernel.org/all/cover.1651348913.git.mchehab@kernel.org/
include/linux/module.h | 8 ++++-- kernel/module/main.c | 65 +++++++++++++++++++++++++++++++++--------- 2 files changed, 56 insertions(+), 17 deletions(-)
diff --git a/include/linux/module.h b/include/linux/module.h index 46d4d5f2516e..3d9d38c426b4 100644 --- a/include/linux/module.h +++ b/include/linux/module.h @@ -620,12 +620,12 @@ extern void __module_get(struct module *module);
/* This is the Right Way to get a module: if it fails, it's being removed, * so pretend it's not there. */ -extern bool try_module_get(struct module *module); +extern bool try_module_get_owner(struct module *module, struct module *this);
extern void module_put(struct module *module);
#else /*!CONFIG_MODULE_UNLOAD*/ -static inline bool try_module_get(struct module *module) +static inline bool try_module_get_owner(struct module *module, struct module *this) { return !module || module_is_live(module); } @@ -740,7 +740,7 @@ static inline void __module_get(struct module *module) { }
-static inline bool try_module_get(struct module *module) +static inline bool try_module_get_owner(struct module *module, struct module *this) { return true; } @@ -875,6 +875,8 @@ static inline bool module_sig_ok(struct module *module) } #endif /* CONFIG_MODULE_SIG */
+#define try_module_get(mod) try_module_get_owner(mod, THIS_MODULE) + int module_kallsyms_on_each_symbol(int (*fn)(void *, const char *, struct module *, unsigned long), void *data); diff --git a/kernel/module/main.c b/kernel/module/main.c index 05a42d8fcd7a..218c4308bb7a 100644 --- a/kernel/module/main.c +++ b/kernel/module/main.c @@ -150,6 +150,24 @@ int unregister_module_notifier(struct notifier_block *nb) } EXPORT_SYMBOL(unregister_module_notifier);
+static bool __try_module_get(struct module *module) +{ + bool ret = true; + + if (module) { + preempt_disable(); + /* Note: here, we can fail to get a reference */ + if (likely(module_is_live(module) && + atomic_inc_not_zero(&module->refcnt) != 0)) + trace_module_get(module, _RET_IP_); + else + ret = false; + + preempt_enable(); + } + return ret; +} + /* * We require a truly strong try_module_get(): 0 means success. * Otherwise an error is returned due to ongoing or failed @@ -160,7 +178,7 @@ static inline int strong_try_module_get(struct module *mod) BUG_ON(mod && mod->state == MODULE_STATE_UNFORMED); if (mod && mod->state == MODULE_STATE_COMING) return -EBUSY; - if (try_module_get(mod)) + if (__try_module_get(mod)) return 0; else return -ENOENT; @@ -631,6 +649,33 @@ static int ref_module(struct module *a, struct module *b) return 0; }
+static int ref_module_dependency(struct module *mod, struct module *this) +{ + int ret; + + if (!this || !this->name) + return -EINVAL; + + if (mod == this) + return 0; + + mutex_lock(&module_mutex); + + ret = ref_module(this, mod); + +#ifdef CONFIG_MODULE_UNLOAD + if (ret) + goto ret; + + ret = sysfs_create_link(mod->holders_dir, + &this->mkobj.kobj, this->name); +#endif + +ret: + mutex_unlock(&module_mutex); + return ret; +} + /* Clear the unload stuff of the module. */ static void module_unload_free(struct module *mod) { @@ -841,24 +886,16 @@ void __module_get(struct module *module) } EXPORT_SYMBOL(__module_get);
-bool try_module_get(struct module *module) +bool try_module_get_owner(struct module *module, struct module *this) { - bool ret = true; + int ret = __try_module_get(module);
- if (module) { - preempt_disable(); - /* Note: here, we can fail to get a reference */ - if (likely(module_is_live(module) && - atomic_inc_not_zero(&module->refcnt) != 0)) - trace_module_get(module, _RET_IP_); - else - ret = false; + if (ret) + ref_module_dependency(module, this);
- preempt_enable(); - } return ret; } -EXPORT_SYMBOL(try_module_get); +EXPORT_SYMBOL(try_module_get_owner);
void module_put(struct module *module) {
Le 30/04/2022 à 22:04, Mauro Carvalho Chehab a écrit :
You may want to remove that useless 'extern'.
'checkpatch --strict' will likely tell you to do so.
What is 'this' ? Can we give it a more precise name ? Is it a child, a parent, a owner, something else ?
Looks like that #ifdef could be avoided and replaced by IS_ENABLED(CONFIG_MODULE_UNLOAD)
Something like:
if (!IS_ENABLED(CONFIG_MODULE_UNLOAD) || ret) goto ret;
Same here, what is 'this' exactly ?
Em Thu, 5 May 2022 23:35:29 +0200 Andi Shyti andi.shyti@linux.intel.com escreveu:
I don't think it should care about the return value, as a failure to create a sysfs node for the holder or to add it to the holders list is not fatal: modules can still continue working without that.
Also, I opted to be conservative here: currently, not creating these doesn't cause try_module_get() to fail. I'm not sure what would be the impact if this starts to fail.
So, right now, I'm opting to just ignore the return value. Perhaps in the future this could a warning (similarly to what sysfs create link does).
Regards, Mauro
Thanks, Mauro
On some devices, the hda driver needs to hook into a video driver, in order to be able to properly access the audio hardware and/or the power management function.
That's the case of several snd_hda_intel devices that depends on i915 driver.
Ensure that a proper reference between the snd-hda driver needing such binding is shown at /proc/modules, in order to allow userspace to know about such binding.
Signed-off-by: Mauro Carvalho Chehab mchehab@kernel.org ---
See [PATCH v5 0/2] at: https://lore.kernel.org/all/cover.1651348913.git.mchehab@kernel.org/
sound/hda/hdac_component.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/sound/hda/hdac_component.c b/sound/hda/hdac_component.c index bb37e7e0bd79..7789873ddf47 100644 --- a/sound/hda/hdac_component.c +++ b/sound/hda/hdac_component.c @@ -199,7 +199,7 @@ static int hdac_component_master_bind(struct device *dev) }
/* pin the module to avoid dynamic unbinding, but only if given */ - if (!try_module_get(acomp->ops->owner)) { + if (!try_module_get_owner(acomp->ops->owner, dev->driver->owner)) { ret = -ENODEV; goto out_unbind; }
On Sat, 30 Apr 2022 22:04:55 +0200, Mauro Carvalho Chehab wrote:
Maybe I was too late to the game (just back from vacation), but FWIW:
Reviewed-by: Takashi Iwai tiwai@suse.de
thanks,
Takashi
dri-devel@lists.freedesktop.org
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Andi Shyti -
Christophe Leroy -
Mauro Carvalho Chehab -
Takashi Iwai