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H A Dtrace_hwlat.cdiff 79250decc9ab0d9ba96dc73106978384c75d5ae0 Tue Sep 24 04:45:14 CDT 2024 Wei Li <liwei391@huawei.com> tracing/hwlat: Fix a race during cpuhp processing

commit 2a13ca2e8abb12ee43ada8a107dadca83f140937 upstream.

The cpuhp online/offline processing race also exists in percpu-mode hwlat
tracer in theory, apply the fix too. That is:

T1 | T2
[CPUHP_ONLINE] | cpu_device_down()
hwlat_hotplug_workfn() |
| cpus_write_lock()
| takedown_cpu(1)
| cpus_write_unlock()
[CPUHP_OFFLINE] |
cpus_read_lock() |
start_kthread(1) |
cpus_read_unlock() |

Cc: stable@vger.kernel.org
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Link: https://lore.kernel.org/20240924094515.3561410-5-liwei391@huawei.com
Fixes: ba998f7d9531 ("trace/hwlat: Support hotplug operations")
Signed-off-by: Wei Li <liwei391@huawei.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>