Hi, When running specjbb on a power7 numa box, I am seeing java threads getting stuck in futex
# ps -Ao pid,tt,user,fname,tmout,f,wchan | grep futex 14808 pts/0 root java - 0 futex_wait_queue_me 14925 pts/0 root java - 0 futex_wait_queue_me # stack traces, I see [ 1843.426591] Call Trace: [ 1843.426595] [c0000017101d74d0] [0000000000000020] 0x20 (unreliable) [ 1843.426601] [c0000017101d76a0] [c000000000014c50] .__switch_to+0x1e0/0x390 [ 1843.426607] [c0000017101d7750] [c0000000006ed314] .__schedule+0x364/0x8c0 [ 1843.426613] [c0000017101d79d0] [c000000000139c28] .futex_wait_queue_me+0xf8/0x1a0 [ 1843.426619] [c0000017101d7a60] [c00000000013afbc] .futex_wait+0x17c/0x2a0 [ 1843.426626] [c0000017101d7c10] [c00000000013cee4] .do_futex+0x254/0xd80 [ 1843.426631] [c0000017101d7d60] [c00000000013db2c] .SyS_futex+0x11c/0x1d0 [ 1843.426638] [c0000017101d7e30] [c000000000009efc] syscall_exit+0x0/0x7c [ 1843.426643] java S 00003fffa08b16a0 0 14812 14203 0x00000080 [ 1843.426650] Call Trace: [ 1843.426653] [c00000170c6034d0] [c000001710b09cf8] 0xc000001710b09cf8 (unreliable) [ 1843.426660] [c00000170c6036a0] [c000000000014c50] .__switch_to+0x1e0/0x390 [ 1843.426666] [c00000170c603750] [c0000000006ed314] .__schedule+0x364/0x8c0 [ 1843.426672] [c00000170c6039d0] [c000000000139c28] .futex_wait_queue_me+0xf8/0x1a0 [ 1843.426679] [c00000170c603a60] [c00000000013afbc] .futex_wait+0x17c/0x2a0 [ 1843.453383] [c00000170c603c10] [c00000000013cee4] .do_futex+0x254/0xd80 [ 1843.453389] [c00000170c603d60] [c00000000013db2c] .SyS_futex+0x11c/0x1d0 [ 1843.453395] [c00000170c603e30] [c000000000009efc] syscall_exit+0x0/0x7c [ 1843.453400] java S 00003fffa08b1a74 0 14813 14203 0x00000080 [ 1843.453407] Call Trace: There are 332 tasks all stuck in futex_wait_queue_me(). I am able to reproduce this consistently. Infact I can reproduce this if the java_constraint is either node, socket, system. However I am not able to reproduce if java_constraint is set to core. I ran git bisect between v3.12 and v3.14-rc6 and found that https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=b0c29f79ecea0b6fbcefc999e70f2843ae8306db commit b0c29f79ecea0b6fbcefc999e70f2843ae8306db Author: Davidlohr Bueso <davidl...@hp.com> Date: Sun Jan 12 15:31:25 2014 -0800 futexes: Avoid taking the hb->lock if there's nothing to wake up was the commit thats causing the threads to be stuck in futex. I reverted b0c29f79ecea0b6fbcefc999e70f2843ae8306db on top of v3.14-rc6 and confirmed that reverting the commit solved the problem. -- Thanks and Regards Srikar Dronamraju _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev