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>

1 files changed, 9 insertions, 0 deletions

diff --git a/include/linux/pid.h b/include/linux/pid.h
index 22921ac4cfd..d7e98ff8021 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 */