Messages in this thread | | | Date | Fri, 8 Aug 2008 15:48:56 -0700 (PDT) | From | David Witbrodt <> | Subject | Re: HPET regression in 2.6.26 versus 2.6.25 |
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OK, suffering from insomnia this morning, I added printk()'s to net/ipv4/af_inet.c in order to find the code where the freeze happens. One of 2 loops was the culprit:
===== BEGIN CODE ======================= #ifdef CONFIG_IP_MULTICAST if (inet_add_protocol(&igmp_protocol, IPPROTO_IGMP) < 0) printk(KERN_CRIT "inet_init: Cannot add IGMP protocol\n"); #endif /* Register the socket-side information for inet_create. */ for (r = &inetsw[0]; r < &inetsw[SOCK_MAX]; ++r) INIT_LIST_HEAD(r);
for (q = inetsw_array; q < &inetsw_array[INETSW_ARRAY_LEN]; ++q) inet_register_protosw(q); /* * Set the ARP module up */ ===== END CODE =======================
Feeling better, I tried to get a few hours of sleep before I had to go to work.
Knowing where to focus more attention, I restored the original version of af_inet.c from the git tree with
git show HEAD:net/ivp4/af_inet.c
and then made the following changes to discover which loop was the problem:
===== BEGIN DIFF ======================== #ifdef CONFIG_IP_MULTICAST if (inet_add_protocol(&igmp_protocol, IPPROTO_IGMP) < 0) printk(KERN_CRIT "inet_init: Cannot add IGMP protocol\n"); #endif + printk(" First loop:\n"); + printk(" SOCK_MAX = %d\n", SOCK_MAX); + int dwindex=0; /* Register the socket-side information for inet_create. */ for (r = &inetsw[0]; r < &inetsw[SOCK_MAX]; ++r) + { + printk(" initializing: &inetsw[%d] = %p\n", dwindex, r); INIT_LIST_HEAD(r); + ++dwindex; + } + printk(" Second loop:\n"); + printk(" INETSW_ARRAY_LEN = %d\n", INETSW_ARRAY_LEN); + printk(" Initial q = %p\n", inetsw_array); + printk(" Final q = %p\n", &inetsw_array[INETSW_ARRAY_LEN]); + dwindex=0; for (q = inetsw_array; q < &inetsw_array[INETSW_ARRAY_LEN]; ++q) + { + printk(" initializing: &q[%d]\n", dwindex); inet_register_protosw(q); + ++dwindex; + } /* * Set the ARP module up */ ===== END DIFF ========================
I then built the kernel, installed it, and rebooted. The following output was observed:
===== BEGIN OUTPUT ======================== ... NET: Registered protocol family 2 First loop: SOCK_MAX = 11 initializing: &initsw[0] = ffffffff809c8460 initializing: &initsw[1] = ffffffff809c8470 initializing: &initsw[2] = ffffffff809c8480 initializing: &initsw[3] = ffffffff809c8490 initializing: &initsw[4] = ffffffff809c84a0 initializing: &initsw[5] = ffffffff809c84b0 initializing: &initsw[6] = ffffffff809c84c0 initializing: &initsw[7] = ffffffff809c84d0 initializing: &initsw[8] = ffffffff809c84e0 initializing: &initsw[9] = ffffffff809c84f0 initializing: &initsw[10] = ffffffff809c8500 Second loop: INETSW_ARRAY_LEN = 3 Initial q = ffffffff806f8a20 Final q = ffffffff806f8a60 initializing: &q[0]
===== END OUTPUT ========================
This is where my kernels (2.6.26* and 2.6.27*) are freezing, in the call of inet_register_protosw().
As I find time, I will keep trying to dig deeper. Hopefully one of you on the LKML has an idea of what's wrong, because even though I am familiar with C and C++ I have no background at all with Linux kernel code itself.
Dave W.
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