Hi, I'm not an expert on this but I've lost some time not long ago trying to understand what was causing that bug message "scheduling while atomic".
My 'short' story: I was trying to trace an issue that I had on my board, so I've enabled the check for 'sleep inside atomic' and I got the spam of 'scheduling while atomic' messages. Without thinking much, I remembered that the gcc toolchain I use doesn't have atomic builtins (it has only been added in gcc-4.7.x for the m68k) so I switched back to the old gcc-4.2.4 toolchain that uses the old m68k ABI (later I realized that kernel has its own code for atomic access), but to my surprise the 'scheduling while atomic' spam was fixed with gcc-4.2.4. After loosing a lot of time comparing the asm from kernel generated with gcc-4.2.4 and gcc-4.5.1, I found nothing that explained the spam. I still don't know what the hell is going on with both gcc's (but is definitively related to it). Maybe something related to memory barriers has changed (or broken ?). Anyway... Digging in the kernel sources and reading some stuff, I concluded that "Sleep inside atomic section checking" doesn't make sense since the m68k arch doesn't support SMP or preemption. >From what I could understand this check looks for scheduling inside spinlocks (that should disable preemption). In my case, since I don't have preemption enabled in the first place, then spinlocks do absolutely nothing (the ones that don't disable irqs). I never bothered again with this, since my kernel works fine and the issue that made me enabled this stupid check, is fixed now. I'm using the latest kernel from Greg m68knommu git (3.8 last time I checked) and my board is based on a dusty (and the father of all) 68000 cpu, not coldfire. TLDR: Searching in the arch/m68k tree I did find some traces of preemption code for coldfire but it seems to be incomplete. Googling also gives me some threads that mention the 'unfinished' preemption support for coldfires. Regards, Luis On Wed, Mar 6, 2013 at 8:18 AM, Christian Gieseler <christiangiese...@yahoo.de> wrote: > Hi Luis, > > Yes you are right i was generalizing too much. With preemption disabled The > Boot Trace with preemption disabled does not show the scheduling while > atomic, but shows a lot of other output with "*** ILLEGAL INSTRUCTION *** > FORMAT=4" and kernel panic in the end. > > The "Sleep inside atomic section checking" option was disabled. If it is > enabled it gives a slightly longer trace (see below). But still I am not > really sure how to tackle this. As we need preemption in the end it seems > better to me to debug with preemption enabled. Or is it easier to get the > kernel running first switch on preemption afterwards to separate possible > issues? > > Regards > Christian > > Bootup with "Sleep inside atomic section checking" enabled: > > BUG: scheduling while atomic: swapper/0/0x00000000 > Modules linked in: > Call Trace: [<401d04b4>] __schedule_bug+0x40/0x52 > [<401d2b0c>] __schedule+0x33e/0x3c0 > [<401d3104>] schedule+0x38/0x54 > [<401d32a4>] schedule_preempt_disabled+0x18/0x24 > [<401cf1c2>] rest_init+0x72/0x82 > [<401d01d0>] printk+0x0/0x20 > [<40252678>] start_kernel+0x2e8/0x2f4 > [<400200da>] _exit+0x0/0x6 > > ------------[ cut here ]------------ > WARNING: at kernel/rcutiny.c:135 rcu_idle_exit_common.part.7+0x56/0x66() > Current pid: 45 comm: kworker/u:1 / Idle pid: 0 comm: swapper > Modules linked in: > Call Trace: [<4002610c>] warn_slowpath_common+0x50/0x6a > [<4004665a>] hrtimer_try_to_cancel+0x0/0xbc > [<400261a4>] warn_slowpath_fmt+0x2a/0x32 > [<400606be>] rcu_idle_exit_common.part.7+0x56/0x66 > [<400606be>] rcu_idle_exit_common.part.7+0x56/0x66 > [<40060a34>] rcu_irq_enter+0x62/0x98 > [<4002dc52>] irq_enter+0xa/0x60 > [<4002081c>] do_IRQ+0x1c/0x3c > [<400233ea>] inthandler+0x2a/0x34 > [<4004665a>] hrtimer_try_to_cancel+0x0/0xbc > [<40046668>] hrtimer_try_to_cancel+0xe/0xbc > [<4004672a>] hrtimer_cancel+0x14/0x30 > [<4002b79a>] do_exit+0x51a/0x888 > [<4002be52>] sys_exit+0x0/0x16 > [<4003ac72>] wait_for_helper+0x0/0x96 > [<4002be68>] do_group_exit+0x0/0xf8 > [<400232d8>] system_call+0x48/0x86 > [<4003ac72>] wait_for_helper+0x0/0x96 > [<40020a90>] kernel_thread+0x3a/0x42 > > ---[ end trace d05fe4c5ce0089d4 ]--- > ------------[ cut here ]------------ > WARNING: at kernel/rcutiny.c:75 > rcu_idle_enter_common.isra.8.part.9+0x6c/0x88() > Current pid: 45 comm: kworker/u:1 / Idle pid: 0 comm: swapper > Modules linked in: > Call Trace: [<4002610c>] warn_slowpath_common+0x50/0x6a > [<400261a4>] warn_slowpath_fmt+0x2a/0x32 > [<40060b6c>] rcu_idle_enter_common.isra.8.part.9+0x6c/0x88 > [<40060b6c>] rcu_idle_enter_common.isra.8.part.9+0x6c/0x88 > [<4004665a>] hrtimer_try_to_cancel+0x0/0xbc > [<40060bd6>] rcu_irq_exit+0x4e/0x98 > [<4002dcda>] irq_exit+0x32/0x60 > [<4002082c>] do_IRQ+0x2c/0x3c > [<400233ea>] inthandler+0x2a/0x34 > [<4004665a>] hrtimer_try_to_cancel+0x0/0xbc > [<40046668>] hrtimer_try_to_cancel+0xe/0xbc > [<4004672a>] hrtimer_cancel+0x14/0x30 > [<4002b79a>] do_exit+0x51a/0x888 > [<4002be52>] sys_exit+0x0/0x16 > [<4003ac72>] wait_for_helper+0x0/0x96 > [<4002be68>] do_group_exit+0x0/0xf8 > [<400232d8>] system_call+0x48/0x86 > [<4003ac72>] wait_for_helper+0x0/0x96 > [<40020a90>] kernel_thread+0x3a/0x42 > > ---[ end trace d05fe4c5ce0089d5 ]--- > libphy: fec_enet_mii_bus: probed > TCP: cubic registered > NET: Registered protocol family 17 > VFS: Mounted root (romfs filesystem) readonly on device 31:0. > Freeing unused kernel memory: 64k freed (0x40252000 - 0x40260000) > > > > -----Original Message----- > From: uclinux-dev-boun...@uclinux.org > [mailto:uclinux-dev-boun...@uclinux.org] On Behalf Of Luis Alves > Sent: Tuesday, March 05, 2013 6:19 PM > To: uClinux development list > Subject: Re: [uClinux-dev] migration issue scheduling while atomic > > Hi, > > With preemption disabled, you shouldn't see that message. > In your current kernel config, under "Kernel hacking" what is the state of > the "Sleep inside atomic section checking" option? > > Regards, > Luis > > > On Tue, Mar 5, 2013 at 5:00 PM, Christian Gieseler > <christiangiese...@yahoo.de> wrote: >> Hi list, >> >> >> >> I ran in another issue while updating our coldfire 5329 board from >> linux >> 2.6.25 to linux 3.6. >> >> >> >> Romfs is mounted as root and then the system says BUG: scheduling >> while >> atomic: swapper/0/0x00000000 and is finally crashing after some trace >> output. >> >> The system is configured to behave a preemptive system (low latency >> desktop) but the system also crashes without preemption activated. >> >> Does somebody know in which direction to look and how to tackle this > issue? >> What is the best way to track it down and fix this? >> >> Let me know if there is more information needed than the boot up >> messages below show. >> >> Best Regards >> >> Christian >> >> >> >> dBUG> dn >> >> Downloading Image 'image.bin' from 192.168.10.254 >> >> TFTP transfer completed >> >> Read 4647940 bytes (9079 blocks) >> >> dBUG> go 0x40020000 >> >> Linux version 3.6.11 (christ...@cglinux.eks-engel.local) (gcc version >> 4.6.1 (Sourcery CodeBench Lite 2011.09-23) ) #72 PREEMPT Tue Mar 5 >> 17:32:05 CET >> 2013 >> >> >> >> >> >> uClinux/COLDFIRE(m532x) >> >> COLDFIRE port done by Greg Ungerer, g...@snapgear.com >> >> Flat model support (C) 1998,1999 Kenneth Albanowski, D. Jeff Dionne >> >> Built 1 zonelists in Zone order, mobility grouping off. Total pages: >> 2024 >> >> Kernel command line: rootfstype=romfs console=tty1 >> console=ttyS0,115200 >> root=/dev/mtdblock0 >> >> PID hash table entries: 64 (order: -5, 256 bytes) >> >> Dentry cache hash table entries: 2048 (order: 0, 8192 bytes) >> >> Inode-cache hash table entries: 2048 (order: 0, 8192 bytes) >> >> Memory available: 11392k/16256k RAM, (1736k kernel code, 631k data) >> >> NR_IRQS:256 >> >> Calibrating delay loop... HZ=100 >> >> 15.46 BogoMIPS (lpj=77312) >> >> pid_max: default: 32768 minimum: 301 >> >> Mount-cache hash table entries: 1024 >> >> NET: Registered protocol family 16 >> >> bio: create slab <bio-0> at 0 >> >> Switching to clocksource tmr >> >> NET: Registered protocol family 2 >> >> TCP established hash table entries: 1024 (order: 0, 8192 bytes) >> >> TCP bind hash table entries: 1024 (order: -1, 4096 bytes) >> >> TCP: Hash tables configured (established 1024 bind 1024) >> >> TCP: reno registered >> >> UDP hash table entries: 512 (order: 0, 8192 bytes) >> >> UDP-Lite hash table entries: 512 (order: 0, 8192 bytes) >> >> NET: Registered protocol family 1 >> >> jffs2: version 2.2. (NAND) C 2001-2006 Red Hat, Inc. >> >> ROMFS MTD (C) 2007 Red Hat, Inc. >> >> msgmni has been set to 22 >> >> io scheduler noop registered >> >> io scheduler deadline registered >> >> io scheduler cfq registered (default) >> >> ColdFire internal UART serial driver >> >> ttyS0 at MMIO 0xfc060000 (irq = 90) is a ColdFire UART >> >> console [ttyS0] enabled >> >> ttyS1 at MMIO 0xfc064000 (irq = 91) is a ColdFire UART >> >> ttyS2 at MMIO 0xfc068000 (irq = 92) is a ColdFire UART >> >> brd: module loaded >> >> uclinux[mtd]: RAM probe address=0x4026fd40 size=0x22c000 >> >> Creating 1 MTD partitions on "RAM": >> >> 0x000000000000-0x00000022c000 : "ROMfs" >> >> el5329 flash device: 1000000 at 0 >> >> el5329 flash: Found 1 x16 devices at 0x0 in 16-bit bank. Manufacturer >> ID >> 0x000001 Chip ID 0x002101 >> >> Amd/Fujitsu Extended Query Table at 0x0040 >> >> Amd/Fujitsu Extended Query version 1.3. >> >> number of CFI chips: 1 >> >> Creating 7 MTD partitions on " el5329 flash": >> >> 0x000000000000-0x000000020000 : "vectors" >> >> 0x000000020000-0x000000040000 : "user_parameters" >> >> 0x000000040000-0x000000060000 : "system_parameters" >> >> 0x000000060000-0x000000100000 : "bootloader" >> >> 0x000000100000-0x000000700000 : "kernel_partition1" >> >> 0x000000700000-0x000000d00000 : "partition2" >> >> 0x000000d00000-0x000001000000 : "user_data" >> >> BUG: scheduling while atomic: swapper/0/0x00000000 >> >> Modules linked in: >> >> Call Trace: [<401cf054>] __schedule_bug+0x40/0x52 >> >> [<401d160e>] __schedule+0x33e/0x3c0 >> >> [<401d1bf0>] schedule+0x38/0x54 >> >> [<401d1d90>] schedule_preempt_disabled+0x18/0x24 >> >> [<401cdd62>] rest_init+0x72/0x82 >> >> [<401ced70>] printk+0x0/0x20 >> >> [<40252678>] start_kernel+0x2e8/0x2f4 >> >> [<400200da>] _exit+0x0/0x6 >> >> >> >> ------------[ cut here ]------------ >> >> WARNING: at kernel/rcutiny.c:135 >> rcu_idle_exit_common.part.8+0x56/0x66() >> >> Current pid: 45 comm: kworker/u:1 / Idle pid: 0 comm: swapper >> >> Modules linked in: >> >> Call Trace: [<400260f8>] warn_slowpath_common+0x50/0x6a >> >> [<40026190>] warn_slowpath_fmt+0x2a/0x32 >> >> [<40060474>] rcu_idle_exit_common.part.8+0x56/0x66 >> >> [<40060474>] rcu_idle_exit_common.part.8+0x56/0x66 >> >> [<400607ea>] rcu_irq_enter+0x62/0x98 >> >> [<4002dbf4>] irq_enter+0xa/0x60 >> >> [<4002081c>] do_IRQ+0x1c/0x3c >> >> [<400233ea>] inthandler+0x2a/0x34 >> >> [<40041e40>] exit_itimers+0x8/0x16e >> >> [<4002b778>] do_exit+0x524/0x888 >> >> [<4002be26>] sys_exit+0x0/0x16 >> >> [<4003ac12>] wait_for_helper+0x0/0x96 >> >> [<4002be3c>] do_group_exit+0x0/0xf8 >> >> [<400232d8>] system_call+0x48/0x86 >> >> [<4003ac12>] wait_for_helper+0x0/0x96 >> >> [<40020a90>] kernel_thread+0x3a/0x42 >> >> >> >> ---[ end trace 6786da2dfad7182c ]--- >> >> ------------[ cut here ]------------ >> >> WARNING: at kernel/rcutiny.c:75 >> rcu_idle_enter_common.isra.9.part.10+0x6c/0x88() >> >> Current pid: 45 comm: kworker/u:1 / Idle pid: 0 comm: swapper >> >> Modules linked in: >> >> Call Trace: [<400260f8>] warn_slowpath_common+0x50/0x6a >> >> [<40026190>] warn_slowpath_fmt+0x2a/0x32 >> >> [<40060922>] rcu_idle_enter_common.isra.9.part.10+0x6c/0x88 >> >> [<40060922>] rcu_idle_enter_common.isra.9.part.10+0x6c/0x88 >> >> [<4006098c>] rcu_irq_exit+0x4e/0x98 >> >> [<4002dc7c>] irq_exit+0x32/0x60 >> >> [<4002082c>] do_IRQ+0x2c/0x3c >> >> [<400233ea>] inthandler+0x2a/0x34 >> >> [<40041e40>] exit_itimers+0x8/0x16e >> >> [<4002b778>] do_exit+0x524/0x888 >> >> [<4002be26>] sys_exit+0x0/0x16 >> >> [<4003ac12>] wait_for_helper+0x0/0x96 >> >> [<4002be3c>] do_group_exit+0x0/0xf8 >> >> [<400232d8>] system_call+0x48/0x86 >> >> [<4003ac12>] wait_for_helper+0x0/0x96 >> >> [<40020a90>] kernel_thread+0x3a/0x42 >> >> >> >> ---[ end trace 6786da2dfad7182d ]--- >> >> libphy: fec_enet_mii_bus: probed >> >> TCP: cubic registered >> >> NET: Registered protocol family 17 >> >> Name=/dev/root, fs=romfs, flags=32769, data=0 >> >> VFS: Mounted root (romfs filesystem) readonly on device 31:0. >> >> Freeing unused kernel memory: 64k freed (0x40252000 - 0x40260000) >> >> >> _______________________________________________ >> uClinux-dev mailing list >> uClinux-dev@uclinux.org >> http://mailman.uclinux.org/mailman/listinfo/uclinux-dev >> This message was resent by uclinux-dev@uclinux.org To unsubscribe see: >> http://mailman.uclinux.org/mailman/options/uclinux-dev > _______________________________________________ > uClinux-dev mailing list > uClinux-dev@uclinux.org > http://mailman.uclinux.org/mailman/listinfo/uclinux-dev > This message was resent by uclinux-dev@uclinux.org To unsubscribe see: > http://mailman.uclinux.org/mailman/options/uclinux-dev > > _______________________________________________ > uClinux-dev mailing list > uClinux-dev@uclinux.org > http://mailman.uclinux.org/mailman/listinfo/uclinux-dev > This message was resent by uclinux-dev@uclinux.org > To unsubscribe see: > http://mailman.uclinux.org/mailman/options/uclinux-dev _______________________________________________ uClinux-dev mailing list uClinux-dev@uclinux.org http://mailman.uclinux.org/mailman/listinfo/uclinux-dev This message was resent by uclinux-dev@uclinux.org To unsubscribe see: http://mailman.uclinux.org/mailman/options/uclinux-dev
