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stm class: Rework policy node fallback 

Currently, if no matching policy node can be found for a trace source,
we'll try to use "default" policy node, then, if that doesn't exist,
we'll pick the first node, in order of creation. If that also fails,
we'll allocate M/C range from the beginning of the device's M/C range.

This makes it difficult to know which node (if any) was used in any
particular case.

In order to make things more deterministic, the new order is as follows:
  * if they supply ID string, use that and nothing else,
  * if they are a task, use their task name (comm),
  * use "default", if it exists,
  * return failure, to let them know there is no suitable rule.

This should provide enough convenience with the "default" catch-all node,
while not leaving *everything* to chance. As a side effect, this relaxes
the requirement of using ioctl() for identification with the possibility of
using task names as policy nodes.

Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Tested-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
hifive-unleashed-5.1
Alexander Shishkin 2018-10-05 15:42:51 +03:00 committed by Greg Kroah-Hartman
parent ba1cb318dc
commit cb6102bd99
3 changed files with 55 additions and 44 deletions
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85
drivers/hwtracing/stm/core.c
View File

@ -293,15 +293,15 @@ static int stm_output_assign(struct stm_device *stm, unsigned int width,
if (width > stm->data->sw_nchannels)
return -EINVAL;
if (policy_node) {
stp_policy_node_get_ranges(policy_node,
&midx, &mend, &cidx, &cend);
} else {
midx = stm->data->sw_start;
cidx = 0;
mend = stm->data->sw_end;
cend = stm->data->sw_nchannels - 1;
}
/* We no longer accept policy_node==NULL here */
if (WARN_ON_ONCE(!policy_node))
return -EINVAL;
/*
* Also, the caller holds reference to policy_node, so it won't
* disappear on us.
*/
stp_policy_node_get_ranges(policy_node, &midx, &mend, &cidx, &cend);
spin_lock(&stm->mc_lock);
spin_lock(&output->lock);
@ -405,19 +405,30 @@ static int stm_char_release(struct inode *inode, struct file *file)
return 0;
}
static int stm_file_assign(struct stm_file *stmf, char *id, unsigned int width)
static int
stm_assign_first_policy(struct stm_device *stm, struct stm_output *output,
char **ids, unsigned int width)
{
struct stm_device *stm = stmf->stm;
int ret;
struct stp_policy_node *pn;
int err, n;
stmf->policy_node = stp_policy_node_lookup(stm, id);
/*
* On success, stp_policy_node_lookup() will return holding the
* configfs subsystem mutex, which is then released in
* stp_policy_node_put(). This allows the pdrv->output_open() in
* stm_output_assign() to serialize against the attribute accessors.
*/
for (n = 0, pn = NULL; ids[n] && !pn; n++)
pn = stp_policy_node_lookup(stm, ids[n]);
ret = stm_output_assign(stm, width, stmf->policy_node, &stmf->output);
if (!pn)
return -EINVAL;
if (stmf->policy_node)
stp_policy_node_put(stmf->policy_node);
err = stm_output_assign(stm, width, pn, output);
return ret;
stp_policy_node_put(pn);
return err;
}
static ssize_t notrace stm_write(struct stm_data *data, unsigned int master,
@ -455,16 +466,21 @@ static ssize_t stm_char_write(struct file *file, const char __user *buf,
count = PAGE_SIZE - 1;
/*
* if no m/c have been assigned to this writer up to this
* point, use "default" policy entry
* If no m/c have been assigned to this writer up to this
* point, try to use the task name and "default" policy entries.
*/
if (!stmf->output.nr_chans) {
err = stm_file_assign(stmf, "default", 1);
char comm[sizeof(current->comm)];
char *ids[] = { comm, "default", NULL };
get_task_comm(comm, current);
err = stm_assign_first_policy(stmf->stm, &stmf->output, ids, 1);
/*
* EBUSY means that somebody else just assigned this
* output, which is just fine for write()
*/
if (err && err != -EBUSY)
if (err)
return err;
}
@ -550,6 +566,7 @@ static int stm_char_policy_set_ioctl(struct stm_file *stmf, void __user *arg)
{
struct stm_device *stm = stmf->stm;
struct stp_policy_id *id;
char *ids[] = { NULL, NULL };
int ret = -EINVAL;
u32 size;
@ -582,7 +599,9 @@ static int stm_char_policy_set_ioctl(struct stm_file *stmf, void __user *arg)
id->width > PAGE_SIZE / stm->data->sw_mmiosz)
goto err_free;
ret = stm_file_assign(stmf, id->id, id->width);
ids[0] = id->id;
ret = stm_assign_first_policy(stmf->stm, &stmf->output, ids,
id->width);
if (ret)
goto err_free;
@ -818,8 +837,8 @@ EXPORT_SYMBOL_GPL(stm_unregister_device);
static int stm_source_link_add(struct stm_source_device *src,
struct stm_device *stm)
{
char *id;
int err;
char *ids[] = { NULL, "default", NULL };
int err = -ENOMEM;
mutex_lock(&stm->link_mutex);
spin_lock(&stm->link_lock);
@ -833,19 +852,13 @@ static int stm_source_link_add(struct stm_source_device *src,
spin_unlock(&stm->link_lock);
mutex_unlock(&stm->link_mutex);
id = kstrdup(src->data->name, GFP_KERNEL);
if (id) {
src->policy_node =
stp_policy_node_lookup(stm, id);
ids[0] = kstrdup(src->data->name, GFP_KERNEL);
if (!ids[0])
goto fail_detach;
kfree(id);
}
err = stm_output_assign(stm, src->data->nr_chans,
src->policy_node, &src->output);
if (src->policy_node)
stp_policy_node_put(src->policy_node);
err = stm_assign_first_policy(stm, &src->output, ids,
src->data->nr_chans);
kfree(ids[0]);
if (err)
goto fail_detach;

12
drivers/hwtracing/stm/policy.c
View File

@ -392,7 +392,7 @@ static struct configfs_subsystem stp_policy_subsys = {
static struct stp_policy_node *
__stp_policy_node_lookup(struct stp_policy *policy, char *s)
{
struct stp_policy_node *policy_node, *ret;
struct stp_policy_node *policy_node, *ret = NULL;
struct list_head *head = &policy->group.cg_children;
struct config_item *item;
char *start, *end = s;
@ -400,10 +400,6 @@ __stp_policy_node_lookup(struct stp_policy *policy, char *s)
if (list_empty(head))
return NULL;
/* return the first entry if everything else fails */
item = list_entry(head->next, struct config_item, ci_entry);
ret = to_stp_policy_node(item);
next:
for (;;) {
start = strsep(&end, "/");
@ -449,13 +445,17 @@ stp_policy_node_lookup(struct stm_device *stm, char *s)
if (policy_node)
config_item_get(&policy_node->group.cg_item);
mutex_unlock(&stp_policy_subsys.su_mutex);
else
mutex_unlock(&stp_policy_subsys.su_mutex);
return policy_node;
}
void stp_policy_node_put(struct stp_policy_node *policy_node)
{
lockdep_assert_held(&stp_policy_subsys.su_mutex);
mutex_unlock(&stp_policy_subsys.su_mutex);
config_item_put(&policy_node->group.cg_item);
}

2
drivers/hwtracing/stm/stm.h
View File

@ -57,7 +57,6 @@ struct stm_output {
struct stm_file {
struct stm_device *stm;
struct stp_policy_node *policy_node;
struct stm_output output;
};
@ -71,7 +70,6 @@ struct stm_source_device {
struct stm_device __rcu *link;
struct list_head link_entry;
/* one output per stm_source device */
struct stp_policy_node *policy_node;
struct stm_output output;
};