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    SubjectRe: [PATCH] rcu/performance: Fix kfree_perf_init() build warning on 32-bit kernels
    On Tue, Jun 02, 2020 at 11:57:51AM +0200, Geert Uytterhoeven wrote:
    > Hi Paul,
    >
    > On Tue, May 26, 2020 at 9:17 PM Paul E. McKenney <paulmck@kernel.org> wrote:
    > > On Tue, May 26, 2020 at 08:27:44PM +0200, Ingo Molnar wrote:
    > > > * tip-bot2 for Joel Fernandes (Google) <tip-bot2@linutronix.de> wrote:
    > > >
    > > > > The following commit has been merged into the core/rcu branch of tip:
    > > > >
    > > > > Commit-ID: f87dc808009ac86c790031627698ef1a34c31e25
    > > > > Gitweb: https://git.kernel.org/tip/f87dc808009ac86c790031627698ef1a34c31e25
    > > > > Author: Joel Fernandes (Google) <joel@joelfernandes.org>
    > > > > AuthorDate: Mon, 16 Mar 2020 12:32:26 -04:00
    > > > > Committer: Paul E. McKenney <paulmck@kernel.org>
    > > > > CommitterDate: Mon, 27 Apr 2020 11:02:50 -07:00
    > > > >
    > > > > rcuperf: Add ability to increase object allocation size
    > > > >
    > > > > This allows us to increase memory pressure dynamically using a new
    > > > > rcuperf boot command line parameter called 'rcumult'.
    > > > >
    > > > > Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
    > > > > Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
    > > > > ---
    > > > > kernel/rcu/rcuperf.c | 5 ++++-
    > > > > 1 file changed, 4 insertions(+), 1 deletion(-)
    > > > >
    > > > > diff --git a/kernel/rcu/rcuperf.c b/kernel/rcu/rcuperf.c
    > > > > index a4a8d09..16dd1e6 100644
    > > > > --- a/kernel/rcu/rcuperf.c
    > > > > +++ b/kernel/rcu/rcuperf.c
    >
    > > > > @@ -722,6 +723,8 @@ kfree_perf_init(void)
    > > > > schedule_timeout_uninterruptible(1);
    > > > > }
    > > > >
    > > > > + pr_alert("kfree object size=%lu\n", kfree_mult * sizeof(struct kfree_obj));
    > > >
    > > > There's a new build warning on certain 32-bit kernel builds due to
    > > > this commit:
    > > >
    > > > In file included from ./include/linux/printk.h:7,
    > > > from ./include/linux/kernel.h:15,
    > > > from kernel/rcu/rcuperf.c:13:
    > > > kernel/rcu/rcuperf.c: In function ‘kfree_perf_init’:
    > > > ./include/linux/kern_levels.h:5:18: warning: format ‘%lu’ expects argument of type ‘long unsigned int’, but argument 2 has type ‘unsigned int’ [-Wformat=]
    > > > 5 | #define KERN_SOH "\001" /* ASCII Start Of Header */
    > > > | ^~~~~~
    > > > ./include/linux/kern_levels.h:9:20: note: in expansion of macro ‘KERN_SOH’
    > > > 9 | #define KERN_ALERT KERN_SOH "1" /* action must be taken immediately */
    > > > | ^~~~~~~~
    > > > ./include/linux/printk.h:295:9: note: in expansion of macro ‘KERN_ALERT’
    > > > 295 | printk(KERN_ALERT pr_fmt(fmt), ##__VA_ARGS__)
    > > > | ^~~~~~~~~~
    > > > kernel/rcu/rcuperf.c:726:2: note: in expansion of macro ‘pr_alert’
    > > > 726 | pr_alert("kfree object size=%lu\n", kfree_mult * sizeof(struct kfree_obj));
    > > > | ^~~~~~~~
    > > > kernel/rcu/rcuperf.c:726:32: note: format string is defined here
    > > > 726 | pr_alert("kfree object size=%lu\n", kfree_mult * sizeof(struct kfree_obj));
    > > > | ~~^
    > > > | |
    > > > | long unsigned int
    > > > | %u
    >
    > This issue is now upstream.
    >
    > > > The reason for the warning is that both kfree_mult and sizeof() are
    > > > 'int' types on 32-bit kernels, while the format string expects a long.
    >
    > sizeof() is of type size_t, which is either unsigned int (32-bit) or
    > unsigned long (64-bit).
    > Hence the result of the multiplication is also of type size_t.
    >
    > > >
    > > > Instead of casting the type to long or tweaking the format string, the
    > > > most straightforward solution is to upgrade kfree_mult to a long.
    > > > Since this depends on CONFIG_RCU_PERF_TEST
    >
    > So the proper fix is Kefeng's patch from April:
    > "[PATCH -next] rcuperf: Fix printk format warning"
    > https://lore.kernel.org/r/20200417040245.66382-1-wangkefeng.wang@huawei.com

    Apologies for not having followed up on this one.

    I applied this commit and sent the pull request, CCing you.

    Thanx, Paul

    > ":"--
    > > Makes sense, and I have queued the patch below, which I am assuming
    > > that you want in the upcoming merge window. If you don't tell me
    > > otherwise, I will send you an urgent pull request later today.
    > > Or, if you just put it directly into -tip yourself:
    > >
    > > Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
    > >
    > > Either way, please let me know.
    > >
    > > > BTW., could we please also rename this code from 'PERF_TEST'/'perf test'
    > > > to 'PERFORMANCE_TEST'/'performance test'? At first glance I always
    > > > mistakenly believe that it's somehow related to perf, while it isn't. =B-)
    > >
    > > Fair enough, especially given that perf was there first and is also way
    > > more heavily used. ;-)
    > >
    > > But I am guessing that this one is OK for the v5.9 merge window.
    > > Either way, I will update as you say.
    > >
    > > Thanx, Paul
    > >
    > > ------------------------------------------------------------------------
    > >
    > > commit 2fbc7d67a2ed108e3ac63296670fecb3a42fddd0
    > > Author: Ingo Molnar <mingo@kernel.org>
    > > Date: Tue May 26 12:10:01 2020 -0700
    > >
    > > rcuperf: Fix kfree_mult to match printk() format
    > >
    > > This commit changes the type of kfree_mult from int to long in order
    > > to match the printk() format on 32-bit systems.
    > >
    > > Reported-by: kbuild test robot <lkp@intel.com>
    > > Signed-off-by: Ingo Molnar <mingo@kernel.org>
    > > Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
    > >
    > > diff --git a/kernel/rcu/rcuperf.c b/kernel/rcu/rcuperf.c
    > > index d906ca9..fb3a1f0 100644
    > > --- a/kernel/rcu/rcuperf.c
    > > +++ b/kernel/rcu/rcuperf.c
    > > @@ -93,7 +93,7 @@ torture_param(bool, shutdown, RCUPERF_SHUTDOWN,
    > > torture_param(int, verbose, 1, "Enable verbose debugging printk()s");
    > > torture_param(int, writer_holdoff, 0, "Holdoff (us) between GPs, zero to disable");
    > > torture_param(int, kfree_rcu_test, 0, "Do we run a kfree_rcu() perf test?");
    > > -torture_param(int, kfree_mult, 1, "Multiple of kfree_obj size to allocate.");
    > > +torture_param(long, kfree_mult, 1, "Multiple of kfree_obj size to allocate.");
    > >
    > > static char *perf_type = "rcu";
    > > module_param(perf_type, charp, 0444);
    >
    > Gr{oetje,eeting}s,
    >
    > Geert
    >
    > --
    > Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
    >
    > In personal conversations with technical people, I call myself a hacker. But
    > when I'm talking to journalists I just say "programmer" or something like that.
    > -- Linus Torvalds

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