Re: [PATCH 24/36] printk: Remove trace_.*_rcuidle() usage
From: Petr Mladek <pmladek@suse.com>
Date: 2022-06-09 09:17:03
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li.kroll@googlemail.com, vgupta@kernel.org, linux-clk@vger.kernel.org, josh@joshtriplett.org, rostedt@goodmis.org, rcu@vger.kernel.org, bp@alien8.de, bcain@quicinc.com, tsbogend@alpha.franken.de, linux-parisc@vger.kernel.org, sudeep.holla@arm.com, shawnguo@kernel.org, davem@davemloft.net, dalias@libc.org, tony@atomide.com, amakhalov@vmware.com, bjorn.andersson@linaro.org, hpa@zytor.com, sparclinux@vger.kernel.org, linux-hexagon@vger.kernel.org, linux-riscv@lists.infradead.org, anton.ivanov@cambridgegreys.com, jonas@southpole.se, yury.norov@gmail.com, richard@nod.at, x86@kernel.org, linux@armlinux.org.uk, mingo@redhat.com, aou@eecs.berkeley.edu, paulmck@kernel.org, hca@linux.ibm.com, stefan.kristiansson@saunalahti.fi, openrisc@lists.librecores.org, paul.walmsley@sifive.com, linux-tegra@vger.kernel.org, namhyung@kernel.org, andriy.shevchenko@linux.intel.com, jpoimboe@kernel.org, jgross@suse.com, monstr@monstr.eu, linux-mips@vger.kernel.org, palmer@dabbelt.com, anup@brainfault.org, ink@ jurassic.park.msu.ru, johannes@sipsolutions.net, linuxppc-dev@lists.ozlabs.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" [off-list ref] On Wed 2022-06-08 16:27:47, Peter Zijlstra wrote:
The problem, per commit fc98c3c8c9dc ("printk: use rcuidle console
tracepoint"), was printk usage from the cpuidle path where RCU was
already disabled.
Per the patches earlier in this series, this is no longer the case.
My understanding is that this series reduces a lot the amount
of code called with RCU disabled. As a result the particular printk()
call mentioned by commit fc98c3c8c9dc ("printk: use rcuidle console
tracepoint") is called with RCU enabled now. Hence this particular
problem is fixed better way now.
But is this true in general?
Does this "prevent" calling printk() a safe way in code with
RCU disabled?
I am not sure if anyone cares. printk() is the best effort
functionality because of the consoles code anyway. Also I wonder
if anyone uses this trace_console().
Therefore if this patch allows to remove some tricky tracing
code then it might be worth it. But if trace_console_rcuidle()
variant is still going to be available then I would keep using it.
Best Regards,
Petr
quoted hunk ↗ jump to hunk
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> --- kernel/printk/printk.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)--- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c@@ -2238,7 +2238,7 @@ static u16 printk_sprint(char *text, u16 } } - trace_console_rcuidle(text, text_len); + trace_console(text, text_len); return text_len; }