From mboxrd@z Thu Jan 1 00:00:00 1970 From: romain.izard.pro@gmail.com (Romain Izard) Date: Mon, 6 Mar 2017 12:28:00 +0100 Subject: Warning on boot on SAMA5D2 with Linux 4.11-rc1 Message-ID: To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Hello, While looking for another issue, I tried Linux 4.11-rc1 on a SAMA5D2 Xplained board. The boot log contains the following warning: [ 0.100000] ------------[ cut here ]------------ [ 0.100000] WARNING: CPU: 0 PID: 1 at ../kernel/time/sched_clock.c:180 sched_clock_register+0x44/0x1e4 [ 0.100000] CPU: 0 PID: 1 Comm: swapper Not tainted 4.11.0-rc1+ #3 [ 0.100000] Hardware name: Atmel SAMA5 [ 0.100000] [] (unwind_backtrace) from [] (show_stack+0x10/0x14) [ 0.100000] [] (show_stack) from [] (__warn+0xe0/0xf8) [ 0.100000] [] (__warn) from [] (warn_slowpath_null+0x20/0x28) [ 0.100000] [] (warn_slowpath_null) from [] (sched_clock_register+0x44/0x1e4) [ 0.100000] [] (sched_clock_register) from [] (tcb_clksrc_init+0x1ac/0x360) [ 0.100000] [] (tcb_clksrc_init) from [] (do_one_initcall+0xb4/0x15c) [ 0.100000] [] (do_one_initcall) from [] (kernel_init_freeable+0x134/0x1c4) [ 0.100000] [] (kernel_init_freeable) from [] (kernel_init+0x8/0x10c) [ 0.100000] [] (kernel_init) from [] (ret_from_fork+0x14/0x3c) [ 0.100000] ---[ end trace 7ce9be9d7cf6f800 ]--- [ 0.100012] sched_clock: 32 bits at 10MHz, resolution 96ns, wraps every 206986376143ns This is related to the following commit: 7b9f1d16e6d1 clocksource/drivers/tcb_clksrc: Use 32 bit tcb as sched_clock When we call sched_clock_register from tcb_clksrc_init from arch_initcall, we are too late as sched expects all the candidates for its clock to be registered before interrupts are enabled. This warning does not prevent the tcb clock from being used. -- Romain Izard