Peter Zijlstra
2022-Jun-08 14:27 UTC
[PATCH 24/36] printk: Remove trace_.*_rcuidle() usage
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.
Signed-off-by: Peter Zijlstra (Intel) <peterz at 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;
}
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> Signed-off-by: Peter Zijlstra (Intel) <peterz at 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; > } >
Sending again. The previous attempt was rejected by several recipients. It was caused by a mail server changes on my side. I am sorry for spamming those who got the 1st mail already. 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> Signed-off-by: Peter Zijlstra (Intel) <peterz at 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; > } >