From c70f34a8ac66c2cb05593ef5760142e5f862a9b4 Mon Sep 17 00:00:00 2001 From: Andrii Nakryiko Date: Wed, 13 May 2020 22:51:37 -0700 Subject: bpf: Fix bpf_iter's task iterator logic task_seq_get_next might stop prematurely if get_pid_task() fails to get task_struct. Failure to do so doesn't mean that there are no more tasks with higher pids. Procfs's iteration algorithm (see next_tgid in fs/proc/base.c) does a retry in such case. After this fix, instead of stopping prematurely after about 300 tasks on my server, bpf_iter program now returns >4000, which sounds much closer to reality. Fixes: eaaacd23910f ("bpf: Add task and task/file iterator targets") Signed-off-by: Andrii Nakryiko Signed-off-by: Alexei Starovoitov Acked-by: Yonghong Song Link: https://lore.kernel.org/bpf/20200514055137.1564581-1-andriin@fb.com --- kernel/bpf/task_iter.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) (limited to 'kernel/bpf') diff --git a/kernel/bpf/task_iter.c b/kernel/bpf/task_iter.c index a9b7264dda08..4dbf2b6035f8 100644 --- a/kernel/bpf/task_iter.c +++ b/kernel/bpf/task_iter.c @@ -27,9 +27,15 @@ static struct task_struct *task_seq_get_next(struct pid_namespace *ns, struct pid *pid; rcu_read_lock(); +retry: pid = idr_get_next(&ns->idr, tid); - if (pid) + if (pid) { task = get_pid_task(pid, PIDTYPE_PID); + if (!task) { + ++*tid; + goto retry; + } + } rcu_read_unlock(); return task; -- cgit v1.2.3