fix setpriority(PRIO_PGRP) thread iterator breakage

When user calls sys_setpriority(PRIO_PGRP ...) on a NPTL style multi-LWP
process, only the task leader of the process is affected, all other
sibling LWP threads didn't receive the setting.  The problem was that the
iterator used in sys_setpriority() only iteartes over one task for each
process, ignoring all other sibling thread.

Introduce a new macro do_each_pid_thread / while_each_pid_thread to walk
each thread of a process.  Convert 4 call sites in {set/get}priority and
ioprio_{set/get}.

Signed-off-by: Ken Chen <kenchen@google.com>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Roland McGrath <roland@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Jens Axboe <jens.axboe@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

3 files changed, 17 insertions, 8 deletions

diff --git a/fs/ioprio.c b/fs/ioprio.c
index c4a1c3c65aac..da3cc460d4df 100644
--- a/fs/ioprio.c
+++ b/fs/ioprio.c
@@ -115,11 +115,11 @@ asmlinkage long sys_ioprio_set(int which, int who, int ioprio)
                                 pgrp = task_pgrp(current);
                         else
                                 pgrp = find_vpid(who);
-                        do_each_pid_task(pgrp, PIDTYPE_PGID, p) {
+                        do_each_pid_thread(pgrp, PIDTYPE_PGID, p) {
                                 ret = set_task_ioprio(p, ioprio);
                                 if (ret)
                                         break;
-                        } while_each_pid_task(pgrp, PIDTYPE_PGID, p);
+                        } while_each_pid_thread(pgrp, PIDTYPE_PGID, p);
                         break;
                 case IOPRIO_WHO_USER:
                         if (!who)
@@ -204,7 +204,7 @@ asmlinkage long sys_ioprio_get(int which, int who)
                                 pgrp = task_pgrp(current);
                         else
                                 pgrp = find_vpid(who);
-                        do_each_pid_task(pgrp, PIDTYPE_PGID, p) {
+                        do_each_pid_thread(pgrp, PIDTYPE_PGID, p) {
                                 tmpio = get_task_ioprio(p);
                                 if (tmpio < 0)
                                         continue;
@@ -212,7 +212,7 @@ asmlinkage long sys_ioprio_get(int which, int who)
                                         ret = tmpio;
                                 else
                                         ret = ioprio_best(ret, tmpio);
-                        } while_each_pid_task(pgrp, PIDTYPE_PGID, p);
+                        } while_each_pid_thread(pgrp, PIDTYPE_PGID, p);
                         break;
                 case IOPRIO_WHO_USER:
                         if (!who)
diff --git a/include/linux/pid.h b/include/linux/pid.h
index 22921ac4cfd9..d7e98ff8021e 100644
--- a/include/linux/pid.h
+++ b/include/linux/pid.h
@@ -161,4 +161,13 @@ pid_t pid_vnr(struct pid *pid);
                         }                                               \
         } while (0)
 
+#define do_each_pid_thread(pid, type, task)                             \
+        do_each_pid_task(pid, type, task) {                             \
+                struct task_struct *tg___ = task;                       \
+                do {
+
+#define while_each_pid_thread(pid, type, task)                          \
+                } while_each_thread(tg___, task);                       \
+                task = tg___;                                           \
+        } while_each_pid_task(pid, type, task)
 #endif /* _LINUX_PID_H */
diff --git a/kernel/sys.c b/kernel/sys.c
index 3dacb00a7f76..038a7bc0901d 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -169,9 +169,9 @@ asmlinkage long sys_setpriority(int which, int who, int niceval)
                                 pgrp = find_vpid(who);
                         else
                                 pgrp = task_pgrp(current);
-                        do_each_pid_task(pgrp, PIDTYPE_PGID, p) {
+                        do_each_pid_thread(pgrp, PIDTYPE_PGID, p) {
                                 error = set_one_prio(p, niceval, error);
-                        } while_each_pid_task(pgrp, PIDTYPE_PGID, p);
+                        } while_each_pid_thread(pgrp, PIDTYPE_PGID, p);
                         break;
                 case PRIO_USER:
                         user = current->user;
@@ -229,11 +229,11 @@ asmlinkage long sys_getpriority(int which, int who)
                                 pgrp = find_vpid(who);
                         else
                                 pgrp = task_pgrp(current);
-                        do_each_pid_task(pgrp, PIDTYPE_PGID, p) {
+                        do_each_pid_thread(pgrp, PIDTYPE_PGID, p) {
                                 niceval = 20 - task_nice(p);
                                 if (niceval > retval)
                                         retval = niceval;
-                        } while_each_pid_task(pgrp, PIDTYPE_PGID, p);
+                        } while_each_pid_thread(pgrp, PIDTYPE_PGID, p);
                         break;
                 case PRIO_USER:
                         user = current->user;