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rcu_read_lock() is not needed in fprobe_entry, but rcu_dereference_check() is used in rhltable_lookup(), which causes suspicious RCU usage warning: WARNING: suspicious RCU usage 6.17.0-rc1-00001-gdfe0d675df82 #1 Tainted: G S ----------------------------- include/linux/rhashtable.h:602 suspicious rcu_dereference_check() usage! ...... stack backtrace: CPU: 1 UID: 0 PID: 4652 Comm: ftracetest Tainted: G S Tainted: [S]=CPU_OUT_OF_SPEC, [I]=FIRMWARE_WORKAROUND Hardware name: Dell Inc. OptiPlex 7040/0Y7WYT, BIOS 1.1.1 10/07/2015 Call Trace: <TASK> dump_stack_lvl+0x7c/0x90 lockdep_rcu_suspicious+0x14f/0x1c0 __rhashtable_lookup+0x1e0/0x260 ? __pfx_kernel_clone+0x10/0x10 fprobe_entry+0x9a/0x450 ? __lock_acquire+0x6b0/0xca0 ? find_held_lock+0x2b/0x80 ? __pfx_fprobe_entry+0x10/0x10 ? __pfx_kernel_clone+0x10/0x10 ? lock_acquire+0x14c/0x2d0 ? __might_fault+0x74/0xc0 function_graph_enter_regs+0x2a0/0x550 ? __do_sys_clone+0xb5/0x100 ? __pfx_function_graph_enter_regs+0x10/0x10 ? _copy_to_user+0x58/0x70 ? __pfx_kernel_clone+0x10/0x10 ? __x64_sys_rt_sigprocmask+0x114/0x180 ? __pfx___x64_sys_rt_sigprocmask+0x10/0x10 ? __pfx_kernel_clone+0x10/0x10 ftrace_graph_func+0x87/0xb0 As we discussed in [1], fix this by using guard(rcu)() in fprobe_entry() to protect the rhltable_lookup() and rhl_for_each_entry_rcu() with rcu_read_lock and suppress this warning. Link: https://lore.kernel.org/all/20250904062729.151931-1-dongml2@chinatelecom.cn/ Link: https://lore.kernel.org/all/20250829021436.19982-1-dongml2@chinatelecom.cn/ [1] Reported-by: kernel test robot <oliver.sang@intel.com> Closes: https://lore.kernel.org/oe-lkp/202508281655.54c87330-lkp@intel.com Fixes: dfe0d675df82 ("tracing: fprobe: use rhltable for fprobe_ip_table") Signed-off-by: Menglong Dong <dongml2@chinatelecom.cn> Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.