Messages in this thread Patch in this message |  | | | Date | Sat, 18 Sep 2010 11:58:37 -0700 | | From | Greg KH <> | | Subject | [073/123] sched: Use rcu in sys_sched_getscheduler/sys_sched_getparam() |
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From: Thomas Gleixner <tglx@linutronix.de>
commit 5fe85be081edf0ac92d83f9c39e0ab5c1371eb82 upstream
read_lock(&tasklist_lock) does not protect sys_sched_getscheduler and sys_sched_getparam() against a concurrent update of the policy or scheduler parameters as do_sched_setscheduler() does not take the tasklist_lock. The accessed integers can be retrieved w/o locking and are snapshots anyway.
Using rcu_read_lock() to protect find_task_by_vpid() and prevent the task struct from going away is not changing the above situation.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Peter Zijlstra <peterz@infradead.org> LKML-Reference: <20091209100706.753790977@linutronix.de> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Mike Galbraith <efault@gmx.de> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de> --- kernel/sched.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) --- a/kernel/sched.c +++ b/kernel/sched.c @@ -6505,7 +6505,7 @@ SYSCALL_DEFINE1(sched_getscheduler, pid_ return -EINVAL; retval = -ESRCH; - read_lock(&tasklist_lock); + rcu_read_lock(); p = find_process_by_pid(pid); if (p) { retval = security_task_getscheduler(p); @@ -6513,7 +6513,7 @@ SYSCALL_DEFINE1(sched_getscheduler, pid_ retval = p->policy | (p->sched_reset_on_fork ? SCHED_RESET_ON_FORK : 0); } - read_unlock(&tasklist_lock); + rcu_read_unlock(); return retval; } @@ -6531,7 +6531,7 @@ SYSCALL_DEFINE2(sched_getparam, pid_t, p if (!param || pid < 0) return -EINVAL; - read_lock(&tasklist_lock); + rcu_read_lock(); p = find_process_by_pid(pid); retval = -ESRCH; if (!p) @@ -6542,7 +6542,7 @@ SYSCALL_DEFINE2(sched_getparam, pid_t, p goto out_unlock; lp.sched_priority = p->rt_priority; - read_unlock(&tasklist_lock); + rcu_read_unlock(); /* * This one might sleep, we cannot do it with a spinlock held ... @@ -6552,7 +6552,7 @@ SYSCALL_DEFINE2(sched_getparam, pid_t, p return retval; out_unlock: - read_unlock(&tasklist_lock); + rcu_read_unlock(); return retval; }
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