From 24507ce81eaf0c34d91f3d1acaa73ee2f796190a Mon Sep 17 00:00:00 2001 From: Andrii Nakryiko Date: Fri, 1 Nov 2024 11:17:54 -0700 Subject: [PATCH] bpf: ensure RCU Tasks Trace GP for sleepable raw tracepoint BPF links Now that kernel supports sleepable tracepoints, the fact that bpf_probe_unregister() is asynchronous, i.e., that it doesn't wait for any in-flight tracepoints to conclude before returning, we now need to delay BPF raw tp link's deallocation and bpf_prog_put() of its underlying BPF program (regardless of program's own sleepable semantics) until after full RCU Tasks Trace GP. With that GP over, we'll have a guarantee that no tracepoint can reach BPF link and thus its BPF program. We use newly added tracepoint_is_faultable() check to know when this RCU Tasks Trace GP is necessary and utilize BPF link's own sleepable flag passed through bpf_link_init_sleepable() initializer. Link: https://lore.kernel.org/20241101181754.782341-3-andrii@kernel.org Tested-by: Jordan Rife Reported-by: Jordan Rife Fixes: a363d27cdbc2 ("tracing: Allow system call tracepoints to handle page faults") Signed-off-by: Andrii Nakryiko Signed-off-by: Steven Rostedt (Google) --- kernel/bpf/syscall.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index 0f5540627911..db2a987504b2 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -35,6 +35,7 @@ #include #include #include +#include #include #include @@ -3845,8 +3846,9 @@ static int bpf_raw_tp_link_attach(struct bpf_prog *prog, err = -ENOMEM; goto out_put_btp; } - bpf_link_init(&link->link, BPF_LINK_TYPE_RAW_TRACEPOINT, - &bpf_raw_tp_link_lops, prog); + bpf_link_init_sleepable(&link->link, BPF_LINK_TYPE_RAW_TRACEPOINT, + &bpf_raw_tp_link_lops, prog, + tracepoint_is_faultable(btp->tp)); link->btp = btp; link->cookie = cookie; -- 2.25.1