The patch titled devcgroup: remove spin_lock() has been added to the -mm tree. Its filename is devcgroup-remove-spin_lock.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/SubmitChecklist when testing your code *** See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find out what to do about this The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/ ------------------------------------------------------ Subject: devcgroup: remove spin_lock() From: Lai Jiangshan <laijs@xxxxxxxxxxxxxx> Since we introduced rcu for read side, spin_lock is used only for update. But we always hold cgroup_lock() when update, so spin_lock() is not need. Additional cleanup: 1) include linux/rcupdate.h explicitly 2) remove unused variable cur_devcgroup in devcgroup_update_access() Signed-off-by: Lai Jiangshan <laijs@xxxxxxxxxxxxxx> Acked-by: "Serge E. Hallyn" <serue@xxxxxxxxxx> Cc: Paul Menage <menage@xxxxxxxxxx> Cc: James Morris <jmorris@xxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- security/device_cgroup.c | 34 +++++----------------------------- 1 file changed, 5 insertions(+), 29 deletions(-) diff -puN security/device_cgroup.c~devcgroup-remove-spin_lock security/device_cgroup.c --- a/security/device_cgroup.c~devcgroup-remove-spin_lock +++ a/security/device_cgroup.c @@ -1,5 +1,5 @@ /* - * dev_cgroup.c - device cgroup subsystem + * device_cgroup.c - device cgroup subsystem * * Copyright 2007 IBM Corp */ @@ -10,6 +10,7 @@ #include <linux/list.h> #include <linux/uaccess.h> #include <linux/seq_file.h> +#include <linux/rcupdate.h> #define ACC_MKNOD 1 #define ACC_READ 2 @@ -22,18 +23,8 @@ /* * whitelist locking rules: - * cgroup_lock() cannot be taken under dev_cgroup->lock. - * dev_cgroup->lock can be taken with or without cgroup_lock(). - * - * modifications always require cgroup_lock - * modifications to a list which is visible require the - * dev_cgroup->lock *and* cgroup_lock() - * walking the list requires dev_cgroup->lock or cgroup_lock(). - * - * reasoning: dev_whitelist_copy() needs to kmalloc, so needs - * a mutex, which the cgroup_lock() is. Since modifying - * a visible list requires both locks, either lock can be - * taken for walking the list. + * hold cgroup_lock() for update/read. + * hold rcu_read_lock() for read. */ struct dev_whitelist_item { @@ -47,7 +38,6 @@ struct dev_whitelist_item { struct dev_cgroup { struct cgroup_subsys_state css; struct list_head whitelist; - spinlock_t lock; }; static inline struct dev_cgroup *css_to_devcgroup(struct cgroup_subsys_state *s) @@ -103,7 +93,6 @@ free_and_exit: /* Stupid prototype - don't bother combining existing entries */ /* * called under cgroup_lock() - * since the list is visible to other tasks, we need the spinlock also */ static int dev_whitelist_add(struct dev_cgroup *dev_cgroup, struct dev_whitelist_item *wh) @@ -114,7 +103,6 @@ static int dev_whitelist_add(struct dev_ if (!whcopy) return -ENOMEM; - spin_lock(&dev_cgroup->lock); list_for_each_entry(walk, &dev_cgroup->whitelist, list) { if (walk->type != wh->type) continue; @@ -130,7 +118,6 @@ static int dev_whitelist_add(struct dev_ if (whcopy != NULL) list_add_tail_rcu(&whcopy->list, &dev_cgroup->whitelist); - spin_unlock(&dev_cgroup->lock); return 0; } @@ -144,14 +131,12 @@ static void whitelist_item_free(struct r /* * called under cgroup_lock() - * since the list is visible to other tasks, we need the spinlock also */ static void dev_whitelist_rm(struct dev_cgroup *dev_cgroup, struct dev_whitelist_item *wh) { struct dev_whitelist_item *walk, *tmp; - spin_lock(&dev_cgroup->lock); list_for_each_entry_safe(walk, tmp, &dev_cgroup->whitelist, list) { if (walk->type == DEV_ALL) goto remove; @@ -169,7 +154,6 @@ remove: call_rcu(&walk->rcu, whitelist_item_free); } } - spin_unlock(&dev_cgroup->lock); } /* @@ -209,7 +193,6 @@ static struct cgroup_subsys_state *devcg } } - spin_lock_init(&dev_cgroup->lock); return &dev_cgroup->css; } @@ -325,15 +308,11 @@ static int parent_has_perm(struct dev_cg { struct cgroup *pcg = childcg->css.cgroup->parent; struct dev_cgroup *parent; - int ret; if (!pcg) return 1; parent = cgroup_to_devcgroup(pcg); - spin_lock(&parent->lock); - ret = may_access_whitelist(parent, wh); - spin_unlock(&parent->lock); - return ret; + return may_access_whitelist(parent, wh); } /* @@ -352,7 +331,6 @@ static int parent_has_perm(struct dev_cg static int devcgroup_update_access(struct dev_cgroup *devcgroup, int filetype, const char *buffer) { - struct dev_cgroup *cur_devcgroup; const char *b; char *endp; int count; @@ -361,8 +339,6 @@ static int devcgroup_update_access(struc if (!capable(CAP_SYS_ADMIN)) return -EPERM; - cur_devcgroup = task_devcgroup(current); - memset(&wh, 0, sizeof(wh)); b = buffer; _ Patches currently in -mm which might be from laijs@xxxxxxxxxxxxxx are linux-next.patch cgroups-fix-probable-race-with-put_css_set-and-find_css_set.patch cgroups-fix-probable-race-with-put_css_set-and-find_css_set-fix.patch devcgroup-remove-spin_lock.patch -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html