I am seeing "rcu_sched_state detected stall on CPU" messages on Alpha architecture with a generic SMP config. Interactive tasks are seen to lock up, with "INFO: task X blocked for more than 120 seconds" in the kernel logs, and eventual kernel oops and panic, on latest 3.2-rc4 and traceable back to 3.0. Bisection between 2.6.39 and 3.0 leads to commit: 09223371deac67d08ca0b70bd18787920284c967 rcu: Use softirq to address performance regression as the first bad commit. Tested on an Alpha ES45 (Titan) with three 1.25 GHz CPUs and 4 GByte memory. Testing procedure is to build git software and run its test suite with -j4 in the make command argument. The CPU stall messages and eventually system lockup is only seen with a generic Alpha config, never with a Titan machine specific config. An example of kernel logs is (this one probably produced when I tried to shutdown the system when it is falling over): [45360.930876] INFO: rcu_sched_state detected stall on CPU 1 (t=798848 jiffies) [45360.931853] INFO: rcu_sched_state detected stalls on CPUs/tasks: { 1} (detected by 0, t=798850 jiffies) [45489.080225] INFO: task umount:17371 blocked for more than 120 seconds. [45489.158350] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. [45489.252100] umount D fffffc00013461ac 0 17371 17368 0x00000000 [45489.336084] fffffc00fdd53db8 fffffc00fdd97bb8 fffffc000108ca1c fffffc00dcc9e800 [45489.422998] fffffc00dcc9e810 fffffc00013b3a5d fffffc000106289c fffffc00ff0dfda8 [45489.519678] 0000000000000000 fffffc000108c81c fffffc0001cd73f0 0000000000000001 [45489.615381] fffffc00010627f0 0000000000000000 fffffc00dcc9e920 fffffc00ff0bf780 [45489.712060] fffffc00010111b8 fffffc00ff0dfda8 fffffc00ff0dfde8 fffffc0001cdaa58 [45489.808740] 0000000000000000 0000000000000000 fffffc0000000000 fffffc0000000000 [45489.907373] Trace: [45489.930810] [<fffffc000108ca1c>] watchdog+0x200/0x27c [45489.991357] [<fffffc000106289c>] kthread+0xac/0xc4 [45490.048974] [<fffffc000108c81c>] watchdog+0x0/0x27c [45490.107568] [<fffffc00010627f0>] kthread+0x0/0xc4 [45490.164209] [<fffffc00010111b8>] kernel_thread+0x28/0x90 [45490.227685] Let me know if any other information is needed to narrow down the problem. Cheers Michael. -- To unsubscribe from this list: send the line "unsubscribe linux-alpha" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html