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From:   Sven Schnelle <svens@linux.ibm.com>
To:     Donghai Qiao <dqiao@redhat.com>
Cc:     akpm@linux-foundation.org, sfr@canb.auug.org.au, arnd@arndb.de,
        peterz@infradead.org, heying24@huawei.com,
        andriy.shevchenko@linux.intel.com, axboe@kernel.dk,
        rdunlap@infradead.org, tglx@linutronix.de, gor@linux.ibm.com,
        donghai.w.qiao@gmail.com, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3 00/11] smp: cross CPU call interface
References: <20220517180326.997129-1-dqiao@redhat.com>
Date:   Wed, 18 May 2022 08:19:43 +0200
In-Reply-To: <20220517180326.997129-1-dqiao@redhat.com> (Donghai Qiao's
        message of "Tue, 17 May 2022 14:03:15 -0400")
Message-ID: <yt9dy1yz1hxc.fsf@linux.ibm.com>
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Donghai Qiao <dqiao@redhat.com> writes:

> The motivation of this patch set is intended to make the existing
> cross CPU call mechanism become a formal interface, more friendly
> to the kernel developers.
>
> For the simplicity self-explanatory less code redundancy and no
> ambiguity, the set of functions below can satisfy any existing
> demand for cross call, at the meantime they still carry over the
> same semantics and the similar parameter lists.
> [..]

With this patchset applied i see the following splat on s390 when the
ftrace selftests are run:

[    1.007231] Running postponed tracer tests:
[    1.007398] Testing tracer function:
[    1.036267] Callback from call_rcu_tasks() invoked.
[    1.117709] BUG: using smp_processor_id() in preemptible [00000000] code: swapper/0/1
[    1.117737] caller is __smp_call_mask_cond+0x42/0x5f8
[    1.117751] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.18.0-rc7-00017-g9cc3e6b66c62 #789
[    1.117760] Hardware name: IBM 3906 M04 704 (z/VM 7.1.0)
[    1.117769] Call Trace:
[    1.117777]  [<000000000f571e54>] dump_stack_lvl+0xac/0x100
[    1.117788]  [<000000000f576eec>] check_preemption_disabled+0xf4/0xf8
[    1.117798]  [<000000000e94eb72>] __smp_call_mask_cond+0x42/0x5f8
[    1.117808]  [<000000000e94f35c>] smp_call_mask_others+0x54/0x70
[    1.117818]  [<000000000e9a8d5e>] ftrace_modify_all_code+0x146/0x170
[    1.117831]  [<000000000e9a8e70>] ftrace_run_update_code+0x30/0x88
[    1.117842]  [<000000000e9ad3a2>] ftrace_startup+0xea/0x1a0
[    1.117852]  [<000000000e9ad498>] register_ftrace_function+0x40/0x88
[    1.117863]  [<000000000e9ccaa8>] function_trace_init+0x90/0x108
[    1.117897]  [<00000000102957aa>] trace_selftest_startup_function+0x6a/0x338
[    1.117910]  [<000000000f56149a>] run_tracer_selftest+0x11a/0x1b0
[    1.117934]  [<0000000010294fe8>] init_trace_selftests+0x90/0x140
[    1.117965]  [<000000000e808aa8>] do_one_initcall+0x78/0x390
[    1.117996]  [<0000000010280804>] do_initcalls+0x12c/0x150
[    1.118009]  [<0000000010280af8>] kernel_init_freeable+0x250/0x290
[    1.118018]  [<000000000f5770de>] kernel_init+0x2e/0x170
[    1.118028]  [<000000000e80b924>] __ret_from_fork+0x3c/0x58
[    1.118038]  [<000000000f5881ea>] ret_from_fork+0xa/0x40
[    1.118049] 2 locks held by swapper/0/1:
[    1.118058]  #0: 000000001012bae0 (trace_types_lock){+.+.}-{3:3}, at: init_trace_selftests+0x30/0x140
[    1.118085]  #1: 000000001012b698 (ftrace_lock){+.+.}-{3:3}, at: register_ftrace_function+0x32/0x88