On 09/02/2013 09:59 PM, Manfred Spraul wrote: > Hi, > > [forgot to cc everyone, thus I'll summarize some mails...] > On 09/02/2013 06:58 AM, Vineet Gupta wrote: >> On 08/31/2013 11:20 PM, Linus Torvalds wrote: >>> Vineet, actual patch for what Davidlohr suggests attached. Can you try it? >>> >>> Linus >> Apologies for late in getting back to this - I was away from my computer for a bit. >> >> Unfortunately, with a quick test, this patch doesn't help. >> FWIW, this is latest mainline (.config attached). >> >> Let me know what diagnostics I can add to help with this. > msgctl08 is a bulk message send/receive test. I had to look at it once > before, then it was a broken hardware: > https://lkml.org/lkml/2008/6/12/365 > This can be ruled out, because it works with 3.10. > > msgctl08 uses pairs of threads: one thread does msgsnd(), the other one > msgrcv(). > There is no synchronization, i.e. the msgsnd() can race ahead until the > kernel buffer is full and then a block with msgrcv() follows or it could > be pairs of alternating msgsnd()/msgrcv() operations. > No special features are used: each pair of threads has it's own message > queues, all messages have type=1. > > Vineet ran strace - and just before the signal from killing msgctl08, > there are only msgsnd()/msgrcv() calls. > Vineet: > a) could you run strace tomorrow again, with '-ttt' as an additional > option? I don't see where exactly it hangs. Yet to do this. > b) Could you check that it is not just a performance regression? > Does ./msgctl08 1000 16 hang, too? Nope that doesn't hang. The minimal configuration that hangs reliably is msgctl 50000 2 With this config there are 3 processes. ... 555 554 root S 1208 0.4 0 0.0 ./msgctl08 50000 2 554 551 root S 1208 0.4 0 0.0 ./msgctl08 50000 2 551 496 root S 1208 0.4 0 0.0 ./msgctl08 50000 2 ... [ARCLinux]$ cat /proc/551/stack [<80aec3c6>] do_wait+0xa02/0xc94 [<80aecad2>] SyS_wait4+0x52/0xa4 [<80ae24fc>] ret_from_system_call+0x0/0x4 [ARCLinux]$ cat /proc/555/stack [<80c2950e>] SyS_msgrcv+0x252/0x420 [<80ae24fc>] ret_from_system_call+0x0/0x4 [ARCLinux]$ cat /proc/554/stack [<80c28c82>] do_msgsnd+0x116/0x35c [<80ae24fc>] ret_from_system_call+0x0/0x4 Is this a case of lost wakeup or some such. I'm running with some more diagnostics and will report soon ... -Vineet -- To unsubscribe from this list: send the line "unsubscribe linux-next" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
