kernel/trace/trace_events_synth.c:47:1: sparse: sparse: symbol 'lastcmd_mutex' was not declared. Should it be static?

[kernel test robot]

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   99ddf2254febae9eab7fb0bcc02c5322243f5c49
commit: 4ccf11c4e8a8e051499d53a12f502196c97a758e tracing/synthetic: Fix races on freeing last_cmd
date:   3 days ago
config: i386-randconfig-s031-20230403 (https://download.01.org/0day-ci/archive/20230406/202304062033.cRStgOuP-lkp@xxxxxxxxx/config)
compiler: gcc-11 (Debian 11.3.0-8) 11.3.0
reproduce:
        # apt-get install sparse
        # sparse version: v0.6.4-39-gce1a6720-dirty
        # https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=4ccf11c4e8a8e051499d53a12f502196c97a758e
        git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
        git fetch --no-tags linus master
        git checkout 4ccf11c4e8a8e051499d53a12f502196c97a758e
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        make W=1 C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__' O=build_dir ARCH=i386 olddefconfig
        make W=1 C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__' O=build_dir ARCH=i386 SHELL=/bin/bash kernel/trace/

If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@xxxxxxxxx>
| Link: https://lore.kernel.org/oe-kbuild-all/202304062033.cRStgOuP-lkp@xxxxxxxxx/

sparse warnings: (new ones prefixed by >>)
>> kernel/trace/trace_events_synth.c:47:1: sparse: sparse: symbol 'lastcmd_mutex' was not declared. Should it be static?
   kernel/trace/trace_events_synth.c:475:68: sparse: sparse: incorrect type in argument 2 (different address spaces) @@     expected void const [noderef] __user *unsafe_addr @@     got char *str_val @@
   kernel/trace/trace_events_synth.c:475:68: sparse:     expected void const [noderef] __user *unsafe_addr
   kernel/trace/trace_events_synth.c:475:68: sparse:     got char *str_val

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