Hi, This appeared in dmesg after $ echo core > /sys/power/pm_test followed by 3 cycles of $ echo mem > /sys/power/state . .config attached. dmesg excerpt (, full ~1MByte available): [ 525.137575] SMP alternatives: switching to SMP code [ 525.137591] Booting processor 1/2 APIC 0x1 [ 530.612383] Initializing CPU#1 [ 530.612383] Calibrating delay using timer specific routine.. 3990.37 BogoMIPS (lpj=7980742) [ 530.612383] CPU: L1 I cache: 32K, L1 D cache: 32K [ 530.612383] CPU: L2 cache: 4096K [ 530.612383] CPU: Physical Processor ID: 0 [ 530.612383] CPU: Processor Core ID: 1 [ 530.612383] Intel(R) Core(TM)2 Duo CPU T7300 @ 2.00GHz stepping 0a [ 525.230956] CPU0 attaching sched-domain: [ 525.230963] domain 0: span 3 [ 525.230966] groups: 1 2 [ 525.230974] CPU1 attaching sched-domain: [ 525.230977] domain 0: span 3 [ 525.230981] groups: 2 1 [ 525.231945] CPU1 is up [ 530.612400] Switched to high resolution mode on CPU 1 [ 530.612423] ------------[ cut here ]------------ [ 530.612428] WARNING: at /home/ka/q/kernel/linux-2.6./git/linux-2.6/kernel/rcupreempt.c:534 rcu_irq_exit+0xa3/0xa8() [ 530.612432] Modules linked in: i915 drm ipt_MASQUERADE iptable_nat nf_nat nf_conntrack_ipv4 xt_state nf_conntrack ipt_REJECT xt_tcpudp iptable_filter ip_tables x_tables bridge llc autofs4 sunrpc ipv6 acpi_cpufreq arc4 snd_hda_intel snd_seq_dummy pcmcia snd_seq_oss snd_seq_midi_event snd_seq fan ecb crypto_blkcipher snd_seq_device snd_pcm_oss snd_mixer_oss snd_pcm snd_timer thermal snd_page_alloc snd_hwdep snd soundcore button battery processor iwl3945 mac80211 ac yenta_socket rsrc_nonstatic pcmcia_core iTCO_wdt iTCO_vendor_support pcspkr rtc_cmos serio_raw cfg80211 joydev tg3 sg sr_mod cdrom usb_storage ata_piix ahci libata sd_mod scsi_mod ext3 jbd mbcache uhci_hcd ohci_hcd ehci_hcd [last unloaded: microcode] [ 530.612524] Pid: 0, comm: swapper Not tainted 2.6.25-rc2 #18 [ 530.612527] [ 530.612529] Call Trace: [ 530.612532] [] warn_on_slowpath+0x58/0x6b [ 530.612560] [] ? enqueue_hrtimer+0xe4/0xf2 [ 530.612571] [] ? hrtimer_start+0x108/0x11a [ 530.612591] [] rcu_irq_exit+0xa3/0xa8 [ 530.612600] [] irq_exit+0x83/0x94 [ 530.612607] [] smp_apic_timer_interrupt+0x3f/0x52 [ 530.612617] [] apic_timer_interrupt+0x66/0x70 [ 530.612621] [] ? :processor:acpi_safe_halt+0x2b/0x3d [ 530.612670] [] ? :processor:acpi_idle_enter_c1+0x37/0x10a [ 530.612688] [] ? :processor:acpi_idle_enter_bm+0x43/0x2a3 [ 530.612703] [] ? cpuidle_idle_call+0x70/0x9e [ 530.612709] [] ? cpuidle_idle_call+0x0/0x9e [ 530.612717] [] ? cpu_idle+0x97/0xdf [ 530.612727] [] ? start_secondary+0x3d2/0x3df [ 530.612752] [ 530.612755] ---[ end trace 0a4cc108f3488c17 ]--- [ 530.616384] ------------[ cut here ]------------ [ 530.616384] WARNING: at /home/ka/q/kernel/linux-2.6./git/linux-2.6/include/linux/rcupreempt.h:99 tick_nohz_restart_sched_tick+0x76/0x166() [ 530.616384] Modules linked in: i915 drm ipt_MASQUERADE iptable_nat nf_nat nf_conntrack_ipv4 xt_state nf_conntrack ipt_REJECT xt_tcpudp iptable_filter ip_tables x_tables bridge llc autofs4 sunrpc ipv6 acpi_cpufreq arc4 snd_hda_intel snd_seq_dummy pcmcia snd_seq_oss snd_seq_midi_event snd_seq fan ecb crypto_blkcipher snd_seq_device snd_pcm_oss snd_mixer_oss snd_pcm snd_timer thermal snd_page_alloc snd_hwdep snd soundcore button battery processor iwl3945 mac80211 ac yenta_socket rsrc_nonstatic pcmcia_core iTCO_wdt iTCO_vendor_support pcspkr rtc_cmos serio_raw cfg80211 joydev tg3 sg sr_mod cdrom usb_storage ata_piix ahci libata sd_mod scsi_mod ext3 jbd mbcache uhci_hcd ohci_hcd ehci_hcd [last unloaded: microcode] [ 530.616384] Pid: 0, comm: swapper Not tainted 2.6.25-rc2 #18 [ 530.616384] [ 530.616384] Call Trace: [ 530.616384] [] warn_on_slowpath+0x58/0x6b [ 530.616384] [] ? __rb_erase_color+0xc3/0x18c [ 530.616384] [] ? getnstimeofday+0x31/0x88 [ 530.616384] [] ? ktime_get_ts+0x46/0x4b [ 530.616384] [] ? ktime_get+0x11/0x42 [ 530.616384] [] tick_nohz_restart_sched_tick+0x76/0x166 [ 530.616384] [] ? cpuidle_idle_call+0x0/0x9e [ 530.616384] [] cpu_idle+0xb7/0xdf [ 530.616384] [] start_secondary+0x3d2/0x3df [ 530.616384] [ 530.616384] ---[ end trace 0a4cc108f3488c17 ]--- [ 530.620401] ------------[ cut here ]------------ [ 530.620405] WARNING: at /home/ka/q/kernel/linux-2.6./git/linux-2.6/include/linux/rcupreempt.h:91 tick_nohz_stop_sched_tick+0x1cc/0x2b6() [ 530.620410] Modules linked in: i915 drm ipt_MASQUERADE iptable_nat nf_nat nf_conntrack_ipv4 xt_state nf_conntrack ipt_REJECT xt_tcpudp iptable_filter ip_tables x_tables bridge llc autofs4 sunrpc ipv6 acpi_cpufreq arc4 snd_hda_intel snd_seq_dummy pcmcia snd_seq_oss snd_seq_midi_event snd_seq fan ecb crypto_blkcipher snd_seq_device snd_pcm_oss snd_mixer_oss snd_pcm snd_timer thermal snd_page_alloc snd_hwdep snd soundcore button battery processor iwl3945 mac80211 ac yenta_socket rsrc_nonstatic pcmcia_core iTCO_wdt iTCO_vendor_support pcspkr rtc_cmos serio_raw cfg80211 joydev tg3 sg sr_mod cdrom usb_storage ata_piix ahci libata sd_mod scsi_mod ext3 jbd mbcache uhci_hcd ohci_hcd ehci_hcd [last unloaded: microcode] [ 530.620487] Pid: 0, comm: swapper Not tainted 2.6.25-rc2 #18 [ 530.620490] [ 530.620491] Call Trace: [ 530.620501] [] warn_on_slowpath+0x58/0x6b [ 530.620518] [] ? hrtimer_get_next_event+0xa3/0xb3 [ 530.620530] [] ? cmp_next_hrtimer_event+0x16/0x87 [ 530.620542] [] ? get_next_timer_interrupt+0x4f/0x5e [ 530.620552] [] tick_nohz_stop_sched_tick+0x1cc/0x2b6 [ 530.620564] [] ? cpuidle_idle_call+0x0/0x9e [ 530.620573] [] cpu_idle+0x1e/0xdf [ 530.620582] [] start_secondary+0x3d2/0x3df [ 530.620606] [ 530.620609] ---[ end trace 0a4cc108f3488c17 ]--- regards, Karsten