From 0c4c9c1fc595c2d8398b6465f0e2ad238f228499 Mon Sep 17 00:00:00 2001 From: Shiju Jose Date: Thu, 2 Feb 2023 18:23:09 +0000 Subject: [PATCH] tracing: Fix poll() and select() do not work on per_cpu trace_pipe and trace_pipe_raw commit 3e46d910d8acf94e5360126593b68bf4fee4c4a1 upstream. poll() and select() on per_cpu trace_pipe and trace_pipe_raw do not work since kernel 6.1-rc6. This issue is seen after the commit 91cd29d9297dab1f8daee5d30a1b0aa35ad5e8f6 ("tracing/ring-buffer: Have polling block on watermark"). This issue is firstly detected and reported, when testing the CXL error events in the rasdaemon and also erified using the test application for poll() and select(). This issue occurs for the per_cpu case, when calling the ring_buffer_poll_wait(), in kernel/trace/ring_buffer.c, with the buffer_percent > 0 and then wait until the percentage of pages are available. The default value set for the buffer_percent is 50 in the kernel/trace/trace.c. As a fix, allow userspace application could set buffer_percent as 0 through the buffer_percent_fops, so that the task will wake up as soon as data is added to any of the specific cpu buffer. Link: https://lore.kernel.org/linux-trace-kernel/20230202182309.742-2-shiju.jose@huawei.com Cc: Cc: Cc: Cc: stable@vger.kernel.org Fixes: 91cd29d9297da ("tracing/ring-buffer: Have polling block on watermark") Signed-off-by: Shiju Jose Signed-off-by: Steven Rostedt (Google) Signed-off-by: Greg Kroah-Hartman --- kernel/trace/trace.c | 3 --- 1 file changed, 3 deletions(-) diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 8b87f1f74e325..306fbe14747bf 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -8298,9 +8298,6 @@ buffer_percent_write(struct file *filp, const char __user *ubuf, if (val > 100) return -EINVAL; - if (!val) - val = 1; - tr->buffer_percent = val; (*ppos)++; -- 2.39.5