| Message ID | 20230717180317.1097590-5-paulmck@kernel.org (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | e820f032fe48290253e7a345574433e129df446f |
| Headers | show |
| Series | Miscellaneous fixes for v6.6 | expand |
On 7/17/23 14:03, Paul E. McKenney wrote: > The rcu_nocb_poll kernel boot parameter is defined via early_param(), > whose parsing functions are invoked from parse_early_param() which > is in turn invoked by setup_arch(), which is very early indeed. It > is invoked so early that the console output timestamps read 0.000000, > in other words, before time begins. > > This use of early_param() means that the rcu_nocb_poll kernel boot > parameter cannot usefully be embedded into the kernel image. Yes, you > can embed it, but setup_boot_config() is invoked from start_kernel() > too late for it to be parsed. > > But it makes no sense to parse this parameter so early. After all, > it cannot do anything until the rcuog kthreads are created, which is > long after rcu_init() time, let alone setup_boot_config() time. > > This commit therefore switches the rcu_nocb_poll kernel boot parameter > from early_param() to __setup(), which allows boot-config parsing of > this parameter, in turn allowing it to be embedded into the kernel image. > > Signed-off-by: Paul E. McKenney <paulmck@kernel.org> > --- > kernel/rcu/tree_nocb.h | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/kernel/rcu/tree_nocb.h b/kernel/rcu/tree_nocb.h > index 43229d2b0c44..5598212d1f27 100644 > --- a/kernel/rcu/tree_nocb.h > +++ b/kernel/rcu/tree_nocb.h > @@ -77,9 +77,9 @@ __setup("rcu_nocbs", rcu_nocb_setup); > static int __init parse_rcu_nocb_poll(char *arg) > { > rcu_nocb_poll = true; > - return 0; > + return 1; > } > -early_param("rcu_nocb_poll", parse_rcu_nocb_poll); > +__setup("rcu_nocb_poll", parse_rcu_nocb_poll); I was trying to see if core_param() could be used. But I am not sure if the RCU offload threads are spawned too early for that. I am Ok with it: Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org> thanks, -Joel > /* > * Don't bother bypassing ->cblist if the call_rcu() rate is low.
diff --git a/kernel/rcu/tree_nocb.h b/kernel/rcu/tree_nocb.h index 43229d2b0c44..5598212d1f27 100644 --- a/kernel/rcu/tree_nocb.h +++ b/kernel/rcu/tree_nocb.h @@ -77,9 +77,9 @@ __setup("rcu_nocbs", rcu_nocb_setup); static int __init parse_rcu_nocb_poll(char *arg) { rcu_nocb_poll = true; - return 0; + return 1; } -early_param("rcu_nocb_poll", parse_rcu_nocb_poll); +__setup("rcu_nocb_poll", parse_rcu_nocb_poll); /* * Don't bother bypassing ->cblist if the call_rcu() rate is low.
The rcu_nocb_poll kernel boot parameter is defined via early_param(), whose parsing functions are invoked from parse_early_param() which is in turn invoked by setup_arch(), which is very early indeed. It is invoked so early that the console output timestamps read 0.000000, in other words, before time begins. This use of early_param() means that the rcu_nocb_poll kernel boot parameter cannot usefully be embedded into the kernel image. Yes, you can embed it, but setup_boot_config() is invoked from start_kernel() too late for it to be parsed. But it makes no sense to parse this parameter so early. After all, it cannot do anything until the rcuog kthreads are created, which is long after rcu_init() time, let alone setup_boot_config() time. This commit therefore switches the rcu_nocb_poll kernel boot parameter from early_param() to __setup(), which allows boot-config parsing of this parameter, in turn allowing it to be embedded into the kernel image. Signed-off-by: Paul E. McKenney <paulmck@kernel.org> --- kernel/rcu/tree_nocb.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)