diff options
| author | Jiri Olsa <jolsa@kernel.org> | 2022-12-15 22:44:30 +0100 |
|---|---|---|
| committer | Daniel Borkmann <daniel@iogearbox.net> | 2022-12-19 22:08:37 +0100 |
| commit | e2bb9e01d589f7fa82573aedd2765ff9b277816a (patch) | |
| tree | 2e4f31e746c2d7efa4abc68daad8030d09166c22 /kernel/trace/bpf_trace.c | |
| parent | f19a4050455aad847fb93f18dc1fe502eb60f989 (diff) | |
bpf: Remove trace_printk_lock
Both bpf_trace_printk and bpf_trace_vprintk helpers use static buffer guarded
with trace_printk_lock spin lock.
The spin lock contention causes issues with bpf programs attached to
contention_begin tracepoint [1][2].
Andrii suggested we could get rid of the contention by using trylock, but we
could actually get rid of the spinlock completely by using percpu buffers the
same way as for bin_args in bpf_bprintf_prepare function.
Adding new return 'buf' argument to struct bpf_bprintf_data and making
bpf_bprintf_prepare to return also the buffer for printk helpers.
[1] https://lore.kernel.org/bpf/CACkBjsakT_yWxnSWr4r-0TpPvbKm9-OBmVUhJb7hV3hY8fdCkw@mail.gmail.com/
[2] https://lore.kernel.org/bpf/CACkBjsaCsTovQHFfkqJKto6S4Z8d02ud1D7MPESrHa1cVNNTrw@mail.gmail.com/
Reported-by: Hao Sun <sunhao.th@gmail.com>
Suggested-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20221215214430.1336195-4-jolsa@kernel.org
Diffstat (limited to 'kernel/trace/bpf_trace.c')
| -rw-r--r-- | kernel/trace/bpf_trace.c | 20 |
1 files changed, 6 insertions, 14 deletions
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c index 2129f7c68bb5..23ce498bca97 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -369,8 +369,6 @@ static const struct bpf_func_proto *bpf_get_probe_write_proto(void) return &bpf_probe_write_user_proto; } -static DEFINE_RAW_SPINLOCK(trace_printk_lock); - #define MAX_TRACE_PRINTK_VARARGS 3 #define BPF_TRACE_PRINTK_SIZE 1024 @@ -380,9 +378,8 @@ BPF_CALL_5(bpf_trace_printk, char *, fmt, u32, fmt_size, u64, arg1, u64 args[MAX_TRACE_PRINTK_VARARGS] = { arg1, arg2, arg3 }; struct bpf_bprintf_data data = { .get_bin_args = true, + .get_buf = true, }; - static char buf[BPF_TRACE_PRINTK_SIZE]; - unsigned long flags; int ret; ret = bpf_bprintf_prepare(fmt, fmt_size, args, @@ -390,11 +387,9 @@ BPF_CALL_5(bpf_trace_printk, char *, fmt, u32, fmt_size, u64, arg1, if (ret < 0) return ret; - raw_spin_lock_irqsave(&trace_printk_lock, flags); - ret = bstr_printf(buf, sizeof(buf), fmt, data.bin_args); + ret = bstr_printf(data.buf, MAX_BPRINTF_BUF, fmt, data.bin_args); - trace_bpf_trace_printk(buf); - raw_spin_unlock_irqrestore(&trace_printk_lock, flags); + trace_bpf_trace_printk(data.buf); bpf_bprintf_cleanup(&data); @@ -434,9 +429,8 @@ BPF_CALL_4(bpf_trace_vprintk, char *, fmt, u32, fmt_size, const void *, args, { struct bpf_bprintf_data data = { .get_bin_args = true, + .get_buf = true, }; - static char buf[BPF_TRACE_PRINTK_SIZE]; - unsigned long flags; int ret, num_args; if (data_len & 7 || data_len > MAX_BPRINTF_VARARGS * 8 || @@ -448,11 +442,9 @@ BPF_CALL_4(bpf_trace_vprintk, char *, fmt, u32, fmt_size, const void *, args, if (ret < 0) return ret; - raw_spin_lock_irqsave(&trace_printk_lock, flags); - ret = bstr_printf(buf, sizeof(buf), fmt, data.bin_args); + ret = bstr_printf(data.buf, MAX_BPRINTF_BUF, fmt, data.bin_args); - trace_bpf_trace_printk(buf); - raw_spin_unlock_irqrestore(&trace_printk_lock, flags); + trace_bpf_trace_printk(data.buf); bpf_bprintf_cleanup(&data); |