Messages in this thread | | | Date | Wed, 8 Jun 2016 09:06:14 +0100 | From | Mel Gorman <> | Subject | Re: [PATCH 1/2] sched/debug: fix 'schedstats=enable' cmdline option |
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On Tue, Jun 07, 2016 at 02:43:16PM -0500, Josh Poimboeuf wrote: > The 'schedstats=enable' option doesn't work, and also produces the > following warning during boot: > > WARNING: CPU: 0 PID: 0 at /home/jpoimboe/git/linux/kernel/jump_label.c:61 static_key_slow_inc+0x8c/0xa0 > static_key_slow_inc used before call to jump_label_init > Modules linked in: > CPU: 0 PID: 0 Comm: swapper Not tainted 4.7.0-rc1+ #25 > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.8.1-20150318_183358- 04/01/2014 > 0000000000000086 3ae3475a4bea95d4 ffffffff81e03da8 ffffffff8143fc83 > ffffffff81e03df8 0000000000000000 ffffffff81e03de8 ffffffff810b1ffb > 0000003d00000096 ffffffff823514d0 ffff88007ff197c8 0000000000000000 > Call Trace: > [<ffffffff8143fc83>] dump_stack+0x85/0xc2 > [<ffffffff810b1ffb>] __warn+0xcb/0xf0 > [<ffffffff810b207f>] warn_slowpath_fmt+0x5f/0x80 > [<ffffffff811e9c0c>] static_key_slow_inc+0x8c/0xa0 > [<ffffffff810e07c6>] static_key_enable+0x16/0x40 > [<ffffffff8216d633>] setup_schedstats+0x29/0x94 > [<ffffffff82148a05>] unknown_bootoption+0x89/0x191 > [<ffffffff810d8617>] parse_args+0x297/0x4b0 > [<ffffffff82148d61>] start_kernel+0x1d8/0x4a9 > [<ffffffff8214897c>] ? set_init_arg+0x55/0x55 > [<ffffffff82148120>] ? early_idt_handler_array+0x120/0x120 > [<ffffffff821482db>] x86_64_start_reservations+0x2f/0x31 > [<ffffffff82148427>] x86_64_start_kernel+0x14a/0x16d > > The problem is that it tries to update the 'sched_schedstats' static key > before jump labels have been initialized. >
Odd, I thought that particular one had been addressed. At least I saw errors like that in other areas before and they got fixed later by ftrace.
> Changing jump_label_init() to be called earlier before > parse_early_param() wouldn't fix it: it would still fail trying to > poke_text() because mm isn't yet initialized. > > Instead, just create a temporary '__sched_schedstats' variable which can > be copied to the static key later during sched_init() after jump labels > have been initialized. > > Fixes: cb2517653fcc ("sched/debug: Make schedstats a runtime tunable that is disabled by default") > Cc: stable@vger.kernel.org > Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com> > --- > kernel/sched/core.c | 26 +++++++++++++++++++++----- > 1 file changed, 21 insertions(+), 5 deletions(-) > > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > index 7f2cae4..385c947 100644 > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -2253,9 +2253,11 @@ int sysctl_numa_balancing(struct ctl_table *table, int write, > #endif > #endif > > +#ifdef CONFIG_SCHEDSTATS > + > DEFINE_STATIC_KEY_FALSE(sched_schedstats); > +static bool __initdata __sched_schedstats = false; >
Initialisation is unnecessary. Otherwise;
Acked-by: Mel Gorman <mgorman@techsingularity.net>
-- Mel Gorman SUSE Labs
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