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deal with the deadlock may occur in stop_machine context. 

we remove the pre_patch_callback/post_unpatch_callback from the
stop_machine context. If a schedule/sleep happend in callbacks while the
process to be scheuded later will send IPI, because all interrupts
are disabled, the machine will trap into a  deadlock in such situation.
So we remove the pre_patch_callback and post_unpatch_callback from
the stop_machine to avoid such situation. On the other hand, to avoid
the race between the patched code and post-patch/pre-unpatch callbacks when
run in parallel, we didn't remove  the post_patch_callback and
pre_unpatch_callback from stop_machine.
This commit is contained in:
zhenjiang.mzj 2020-07-28 10:33:26 +08:00
parent 3f885dedf5
commit b311112702
1 changed files with 30 additions and 27 deletions
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57
kmod/core/core.c
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@ -377,16 +377,6 @@ static int kpatch_apply_patch(void *data)
return ret;
}
/* run any user-defined pre-patch callbacks */
list_for_each_entry(object, &kpmod->objects, list) {
ret = pre_patch_callback(object);
if (ret) {
pr_err("pre-patch callback failed!\n");
kpatch_state_finish(KPATCH_STATE_FAILURE);
goto err;
}
}
/* tentatively add the new funcs to the global func hash */
do_for_each_linked_func(kpmod, func) {
hash_add_rcu(kpatch_func_hash, &func->node, func->old_addr);
@ -408,8 +398,7 @@ static int kpatch_apply_patch(void *data)
hash_del_rcu(&func->node);
} while_for_each_linked_func();
ret = -EBUSY;
goto err;
return -EBUSY;
}
/*
@ -430,12 +419,6 @@ static int kpatch_apply_patch(void *data)
post_patch_callback(object);
return 0;
err:
/* undo pre-patch callbacks by calling post-unpatch counterparts */
list_for_each_entry(object, &kpmod->objects, list)
post_unpatch_callback(object);
return ret;
}
/* Called from stop_machine */
@ -468,10 +451,6 @@ static int kpatch_remove_patch(void *data)
hash_del_rcu(&func->node);
} while_for_each_linked_func();
/* run any user-defined post-unpatch callbacks */
list_for_each_entry(object, &kpmod->objects, list)
post_unpatch_callback(object);
return 0;
err:
@ -1086,11 +1065,30 @@ int kpatch_register(struct kpatch_module *kpmod, bool replace)
kpatch_state_updating();
/*
* Idle the CPUs, verify activeness safety, and atomically make the new
* functions visible to the ftrace handler.
*/
ret = stop_machine(kpatch_apply_patch, &args, NULL);
/* run any user-defined pre-patch callbacks */
list_for_each_entry(object, &kpmod->objects, list) {
ret = pre_patch_callback(object);
if(ret){
pr_err("pre-patch callback failed!\n");
kpatch_state_finish(KPATCH_STATE_FAILURE);
break;
}
}
/* if pre_patch_callback succeed. */
if (!ret) {
/*
* Idle the CPUs, verify activeness safety, and atomically make the new
* functions visible to the ftrace handler.
*/
ret = stop_machine(kpatch_apply_patch, &args, NULL);
}
/* if pre_patch_callback or stop_machine failed */
if (ret) {
list_for_each_entry(object, &kpmod->objects, list)
post_unpatch_callback(object);
}
/*
* For the replace case, remove any obsolete funcs from the ftrace
@ -1224,6 +1222,11 @@ int kpatch_unregister(struct kpatch_module *kpmod)
ret = stop_machine(kpatch_remove_patch, kpmod, NULL);
if (!ret) {
/* run any user-defined post-unpatch callbacks */
list_for_each_entry(object, &kpmod->objects, list)
post_unpatch_callback(object);
}
/* NMI handlers can return to normal now */
kpatch_state_idle();