tracing: Zero the pipe cpumask on alloc to avoid spurious -EBUSY

The pipe cpumask used to serialize opens between the main and percpu
trace pipes is not zeroed or initialized. This can result in
spurious -EBUSY returns if underlying memory is not fully zeroed.
This has been observed by immediate failure to read the main
trace_pipe file on an otherwise newly booted and idle system:

 # cat /sys/kernel/debug/tracing/trace_pipe
 cat: /sys/kernel/debug/tracing/trace_pipe: Device or resource busy

Zero the allocation of pipe_cpumask to avoid the problem.

Link: https://lore.kernel.org/linux-trace-kernel/[email protected]

Cc: [email protected]
Fixes: c2489bb7e6be ("tracing: Introduce pipe_cpumask to avoid race on trace_pipes")
Reviewed-by: Zheng Yejian <[email protected]>
Reviewed-by: Masami Hiramatsu (Google) <[email protected]>
Signed-off-by: Brian Foster <[email protected]>
Signed-off-by: Steven Rostedt (Google) <[email protected]>

0 files changed, 0 insertions, 0 deletions