Hi Eric, I think I remembered from a previous discussion about this topic, that it was unclear if the rw_semaphores are working the same in RT-Linux. Will this fix work in RT as well?
On 12/3/20 9:12 PM, Eric W. Biederman wrote: > --- a/kernel/kcmp.c > +++ b/kernel/kcmp.c > @@ -70,25 +70,25 @@ get_file_raw_ptr(struct task_struct *task, unsigned int > idx) > return file; > } > > -static void kcmp_unlock(struct mutex *m1, struct mutex *m2) > +static void kcmp_unlock(struct rw_semaphore *l1, struct rw_semaphore *l2) > { > - if (likely(m2 != m1)) > - mutex_unlock(m2); > - mutex_unlock(m1); > + if (likely(l2 != l1)) is this still necessary ? > + up_read(l2); > + up_read(l1); > } > > -static int kcmp_lock(struct mutex *m1, struct mutex *m2) > +static int kcmp_lock(struct rw_semaphore *l1, struct rw_semaphore *l2) > { > int err; > > - if (m2 > m1) > - swap(m1, m2); > + if (l2 > l1) > + swap(l1, l2); and this is probably also no longer necessary? > > - err = mutex_lock_killable(m1); > - if (!err && likely(m1 != m2)) { > - err = mutex_lock_killable_nested(m2, SINGLE_DEPTH_NESTING); > + err = down_read_killable(l1); > + if (!err && likely(l1 != l2)) { and this can now be unconditionally, right? > + err = down_read_killable_nested(l2, SINGLE_DEPTH_NESTING); > if (err) > - mutex_unlock(m1); > + up_read(l1); > } > > return err; > @@ -156,8 +156,8 @@ SYSCALL_DEFINE5(kcmp, pid_t, pid1, pid_t, pid2, int, type, > /* > * One should have enough rights to inspect task details. > */ > - ret = kcmp_lock(&task1->signal->exec_update_mutex, > - &task2->signal->exec_update_mutex); > + ret = kcmp_lock(&task1->signal->exec_update_lock, > + &task2->signal->exec_update_lock); > if (ret) > goto err; > if (!ptrace_may_access(task1, PTRACE_MODE_READ_REALCREDS) || > @@ -212,8 +212,8 @@ SYSCALL_DEFINE5(kcmp, pid_t, pid1, pid_t, pid2, int, type, > } > > err_unlock: > - kcmp_unlock(&task1->signal->exec_update_mutex, > - &task2->signal->exec_update_mutex); > + kcmp_unlock(&task1->signal->exec_update_lock, > + &task2->signal->exec_update_lock); > err: > put_task_struct(task1); > put_task_struct(task2); Thanks Bernd.