* [PATCH v3] kernel/module.c: Only return -EEXIST for modules that have finished loading
@ 2019-05-29 11:26 Prarit Bhargava
2019-06-04 14:29 ` Jessica Yu
0 siblings, 1 reply; 2+ messages in thread
From: Prarit Bhargava @ 2019-05-29 11:26 UTC (permalink / raw)
To: linux-kernel
Cc: Prarit Bhargava, Barret Rhoden, David Arcari, Jessica Yu, Heiko Carstens
Microsoft HyperV disables the X86_FEATURE_SMCA bit on AMD systems, and
linux guests boot with repeated errors:
amd64_edac_mod: Unknown symbol amd_unregister_ecc_decoder (err -2)
amd64_edac_mod: Unknown symbol amd_register_ecc_decoder (err -2)
amd64_edac_mod: Unknown symbol amd_report_gart_errors (err -2)
amd64_edac_mod: Unknown symbol amd_unregister_ecc_decoder (err -2)
amd64_edac_mod: Unknown symbol amd_register_ecc_decoder (err -2)
amd64_edac_mod: Unknown symbol amd_report_gart_errors (err -2)
The warnings occur because the module code erroneously returns -EEXIST
for modules that have failed to load and are in the process of being
removed from the module list.
module amd64_edac_mod has a dependency on module edac_mce_amd. Using
modules.dep, systemd will load edac_mce_amd for every request of
amd64_edac_mod. When the edac_mce_amd module loads, the module has
state MODULE_STATE_UNFORMED and once the module load fails and the state
becomes MODULE_STATE_GOING. Another request for edac_mce_amd module
executes and add_unformed_module() will erroneously return -EEXIST even
though the previous instance of edac_mce_amd has MODULE_STATE_GOING.
Upon receiving -EEXIST, systemd attempts to load amd64_edac_mod, which
fails because of unknown symbols from edac_mce_amd.
add_unformed_module() must wait to return for any case other than
MODULE_STATE_LIVE to prevent a race between multiple loads of
dependent modules.
Signed-off-by: Prarit Bhargava <prarit@redhat.com>
Signed-off-by: Barret Rhoden <brho@google.com>
Cc: David Arcari <darcari@redhat.com>
Cc: Jessica Yu <jeyu@kernel.org>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
---
kernel/module.c | 6 ++----
1 file changed, 2 insertions(+), 4 deletions(-)
diff --git a/kernel/module.c b/kernel/module.c
index 6e6712b3aaf5..1e7dcbe527af 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -3397,8 +3397,7 @@ static bool finished_loading(const char *name)
sched_annotate_sleep();
mutex_lock(&module_mutex);
mod = find_module_all(name, strlen(name), true);
- ret = !mod || mod->state == MODULE_STATE_LIVE
- || mod->state == MODULE_STATE_GOING;
+ ret = !mod || mod->state == MODULE_STATE_LIVE;
mutex_unlock(&module_mutex);
return ret;
@@ -3588,8 +3587,7 @@ static int add_unformed_module(struct module *mod)
mutex_lock(&module_mutex);
old = find_module_all(mod->name, strlen(mod->name), true);
if (old != NULL) {
- if (old->state == MODULE_STATE_COMING
- || old->state == MODULE_STATE_UNFORMED) {
+ if (old->state != MODULE_STATE_LIVE) {
/* Wait in case it fails to load. */
mutex_unlock(&module_mutex);
err = wait_event_interruptible(module_wq,
--
2.21.0
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH v3] kernel/module.c: Only return -EEXIST for modules that have finished loading
2019-05-29 11:26 [PATCH v3] kernel/module.c: Only return -EEXIST for modules that have finished loading Prarit Bhargava
@ 2019-06-04 14:29 ` Jessica Yu
0 siblings, 0 replies; 2+ messages in thread
From: Jessica Yu @ 2019-06-04 14:29 UTC (permalink / raw)
To: Prarit Bhargava; +Cc: linux-kernel, Barret Rhoden, David Arcari, Heiko Carstens
+++ Prarit Bhargava [29/05/19 07:26 -0400]:
>Microsoft HyperV disables the X86_FEATURE_SMCA bit on AMD systems, and
>linux guests boot with repeated errors:
>
>amd64_edac_mod: Unknown symbol amd_unregister_ecc_decoder (err -2)
>amd64_edac_mod: Unknown symbol amd_register_ecc_decoder (err -2)
>amd64_edac_mod: Unknown symbol amd_report_gart_errors (err -2)
>amd64_edac_mod: Unknown symbol amd_unregister_ecc_decoder (err -2)
>amd64_edac_mod: Unknown symbol amd_register_ecc_decoder (err -2)
>amd64_edac_mod: Unknown symbol amd_report_gart_errors (err -2)
>
>The warnings occur because the module code erroneously returns -EEXIST
>for modules that have failed to load and are in the process of being
>removed from the module list.
>
>module amd64_edac_mod has a dependency on module edac_mce_amd. Using
>modules.dep, systemd will load edac_mce_amd for every request of
>amd64_edac_mod. When the edac_mce_amd module loads, the module has
>state MODULE_STATE_UNFORMED and once the module load fails and the state
>becomes MODULE_STATE_GOING. Another request for edac_mce_amd module
>executes and add_unformed_module() will erroneously return -EEXIST even
>though the previous instance of edac_mce_amd has MODULE_STATE_GOING.
>Upon receiving -EEXIST, systemd attempts to load amd64_edac_mod, which
>fails because of unknown symbols from edac_mce_amd.
>
>add_unformed_module() must wait to return for any case other than
>MODULE_STATE_LIVE to prevent a race between multiple loads of
>dependent modules.
>
>Signed-off-by: Prarit Bhargava <prarit@redhat.com>
>Signed-off-by: Barret Rhoden <brho@google.com>
>Cc: David Arcari <darcari@redhat.com>
>Cc: Jessica Yu <jeyu@kernel.org>
>Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Applied. Thanks!
Jessica
>---
> kernel/module.c | 6 ++----
> 1 file changed, 2 insertions(+), 4 deletions(-)
>
>diff --git a/kernel/module.c b/kernel/module.c
>index 6e6712b3aaf5..1e7dcbe527af 100644
>--- a/kernel/module.c
>+++ b/kernel/module.c
>@@ -3397,8 +3397,7 @@ static bool finished_loading(const char *name)
> sched_annotate_sleep();
> mutex_lock(&module_mutex);
> mod = find_module_all(name, strlen(name), true);
>- ret = !mod || mod->state == MODULE_STATE_LIVE
>- || mod->state == MODULE_STATE_GOING;
>+ ret = !mod || mod->state == MODULE_STATE_LIVE;
> mutex_unlock(&module_mutex);
>
> return ret;
>@@ -3588,8 +3587,7 @@ static int add_unformed_module(struct module *mod)
> mutex_lock(&module_mutex);
> old = find_module_all(mod->name, strlen(mod->name), true);
> if (old != NULL) {
>- if (old->state == MODULE_STATE_COMING
>- || old->state == MODULE_STATE_UNFORMED) {
>+ if (old->state != MODULE_STATE_LIVE) {
> /* Wait in case it fails to load. */
> mutex_unlock(&module_mutex);
> err = wait_event_interruptible(module_wq,
>--
>2.21.0
>
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