proc: task_state: move the main seq_printf() outside of rcu_read_lock()

task_state() does seq_printf() under rcu_read_lock(), but this is only
needed for task_tgid_nr_ns() and task_numa_group_id().  We can calculate
tgid/ngid and drop rcu lock.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: Aaron Tomlin <atomlin@redhat.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>,
Cc: Sterling Alexander <stalexan@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Roland McGrath <roland@hack.frob.com>
Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/proc/array.c b/fs/proc/array.c
index 7c8d9ae..800e30f 100644 (file)
--- a/fs/proc/array.c
+++ b/fs/proc/array.c
@@ -158,7 +158,7 @@ static inline void task_state(struct seq_file *m, struct pid_namespace *ns,
        struct group_info *group_info;
        int g;
        const struct cred *cred;
-       pid_t ppid, tpid;
+       pid_t ppid, tpid, tgid, ngid;
        unsigned int max_fds = 0;
 
        rcu_read_lock();
@@ -170,12 +170,16 @@ static inline void task_state(struct seq_file *m, struct pid_namespace *ns,
                if (tracer)
                        tpid = task_pid_nr_ns(tracer, ns);
        }
+
+       tgid = task_tgid_nr_ns(p, ns);
+       ngid = task_numa_group_id(p);
        cred = get_task_cred(p);
 
        task_lock(p);
        if (p->files)
                max_fds = files_fdtable(p->files)->max_fds;
        task_unlock(p);
+       rcu_read_unlock();
 
        seq_printf(m,
                "State:\t%s\n"
@@ -188,10 +192,7 @@ static inline void task_state(struct seq_file *m, struct pid_namespace *ns,
                "Gid:\t%d\t%d\t%d\t%d\n"
                "FDSize:\t%d\nGroups:\t",
                get_task_state(p),
-               task_tgid_nr_ns(p, ns),
-               task_numa_group_id(p),
-               pid_nr_ns(pid, ns),
-               ppid, tpid,
+               tgid, ngid, pid_nr_ns(pid, ns), ppid, tpid,
                from_kuid_munged(user_ns, cred->uid),
                from_kuid_munged(user_ns, cred->euid),
                from_kuid_munged(user_ns, cred->suid),
@@ -201,7 +202,6 @@ static inline void task_state(struct seq_file *m, struct pid_namespace *ns,
                from_kgid_munged(user_ns, cred->sgid),
                from_kgid_munged(user_ns, cred->fsgid),
                max_fds);
-       rcu_read_unlock();
 
        group_info = cred->group_info;
        for (g = 0; g < group_info->ngroups; g++)