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s390/debug: fix debug area life cycle

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[ Upstream commit 9372a82892c2caa6bccab9a4081166fa769699f8 ]

Currently allocation and registration of s390dbf debug areas are tied
together. As a result, a debug area cannot be unregistered and
re-registered while any process has an associated debugfs file open.

Fix this by splitting alloc/release from register/unregister.

Signed-off-by: Peter Oberparleiter <oberpar@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Peter Oberparleiter 2021-08-13 15:05:03 +02:00 committed by Greg Kroah-Hartman
parent 0980d2b21f
commit 86f9980909
1 changed files with 56 additions and 46 deletions
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102
arch/s390/kernel/debug.c
View File

@ -314,24 +314,6 @@ static debug_info_t *debug_info_create(const char *name, int pages_per_area,
goto out;
rc->mode = mode & ~S_IFMT;
/* create root directory */
rc->debugfs_root_entry = debugfs_create_dir(rc->name,
debug_debugfs_root_entry);
/* append new element to linked list */
if (!debug_area_first) {
/* first element in list */
debug_area_first = rc;
rc->prev = NULL;
} else {
/* append element to end of list */
debug_area_last->next = rc;
rc->prev = debug_area_last;
}
debug_area_last = rc;
rc->next = NULL;
refcount_set(&rc->ref_count, 1);
out:
return rc;
@ -391,27 +373,10 @@ static void debug_info_get(debug_info_t *db_info)
*/
static void debug_info_put(debug_info_t *db_info)
{
int i;
if (!db_info)
return;
if (refcount_dec_and_test(&db_info->ref_count)) {
for (i = 0; i < DEBUG_MAX_VIEWS; i++) {
if (!db_info->views[i])
continue;
debugfs_remove(db_info->debugfs_entries[i]);
}
debugfs_remove(db_info->debugfs_root_entry);
if (db_info == debug_area_first)
debug_area_first = db_info->next;
if (db_info == debug_area_last)
debug_area_last = db_info->prev;
if (db_info->prev)
db_info->prev->next = db_info->next;
if (db_info->next)
db_info->next->prev = db_info->prev;
if (refcount_dec_and_test(&db_info->ref_count))
debug_info_free(db_info);
}
}
/*
@ -635,6 +600,31 @@ static int debug_close(struct inode *inode, struct file *file)
return 0; /* success */
}
/* Create debugfs entries and add to internal list. */
static void _debug_register(debug_info_t *id)
{
/* create root directory */
id->debugfs_root_entry = debugfs_create_dir(id->name,
debug_debugfs_root_entry);
/* append new element to linked list */
if (!debug_area_first) {
/* first element in list */
debug_area_first = id;
id->prev = NULL;
} else {
/* append element to end of list */
debug_area_last->next = id;
id->prev = debug_area_last;
}
debug_area_last = id;
id->next = NULL;
debug_register_view(id, &debug_level_view);
debug_register_view(id, &debug_flush_view);
debug_register_view(id, &debug_pages_view);
}
/**
* debug_register_mode() - creates and initializes debug area.
*
@ -664,19 +654,16 @@ debug_info_t *debug_register_mode(const char *name, int pages_per_area,
if ((uid != 0) || (gid != 0))
pr_warn("Root becomes the owner of all s390dbf files in sysfs\n");
BUG_ON(!initialized);
mutex_lock(&debug_mutex);
/* create new debug_info */
rc = debug_info_create(name, pages_per_area, nr_areas, buf_size, mode);
if (!rc)
goto out;
debug_register_view(rc, &debug_level_view);
debug_register_view(rc, &debug_flush_view);
debug_register_view(rc, &debug_pages_view);
out:
if (!rc)
if (rc) {
mutex_lock(&debug_mutex);
_debug_register(rc);
mutex_unlock(&debug_mutex);
} else {
pr_err("Registering debug feature %s failed\n", name);
mutex_unlock(&debug_mutex);
}
return rc;
}
EXPORT_SYMBOL(debug_register_mode);
@ -705,6 +692,27 @@ debug_info_t *debug_register(const char *name, int pages_per_area,
}
EXPORT_SYMBOL(debug_register);
/* Remove debugfs entries and remove from internal list. */
static void _debug_unregister(debug_info_t *id)
{
int i;
for (i = 0; i < DEBUG_MAX_VIEWS; i++) {
if (!id->views[i])
continue;
debugfs_remove(id->debugfs_entries[i]);
}
debugfs_remove(id->debugfs_root_entry);
if (id == debug_area_first)
debug_area_first = id->next;
if (id == debug_area_last)
debug_area_last = id->prev;
if (id->prev)
id->prev->next = id->next;
if (id->next)
id->next->prev = id->prev;
}
/**
* debug_unregister() - give back debug area.
*
@ -718,8 +726,10 @@ void debug_unregister(debug_info_t *id)
if (!id)
return;
mutex_lock(&debug_mutex);
debug_info_put(id);
_debug_unregister(id);
mutex_unlock(&debug_mutex);
debug_info_put(id);
}
EXPORT_SYMBOL(debug_unregister);