[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] DomU's network interface will hung when Dom0 running 32bit
On Sat, Oct 12, 2013 at 04:53:18PM +0800, jianhai luan wrote: > Hi Ian, > I meet the DomU's network interface hung issue recently, and have > been working on the issue from that time. I find that DomU's network > interface, which send lesser package, will hung if Dom0 running > 32bit and DomU's up-time is very long. I think that one jiffies > overflow bug exist in the function tx_credit_exceeded(). > I know the inline function time_after_eq(a,b) will process jiffies > overflow, but the function have one limit a should little that (b + > MAX_SIGNAL_LONG). If a large than the value, time_after_eq will > return false. The MAX_SINGNAL_LONG should be 0x7fffffff at 32-bit > machine. > If DomU's network interface send lesser package (<0.5k/s if > jiffies=250 and credit_bytes=ULONG_MAX), jiffies will beyond out > (credit_timeout.expires + MAX_SIGNAL_LONG) and time_after_eq(now, > next_credit) will failure (should be true). So one timer which will > not be trigger in short time, and later process will be aborted when > timer_pending(&vif->credit_timeout) is true. The result will be > DomU's network interface will be hung in long time (> 40days). > Please think about the below scenario: > Condition: > Dom0 running 32-bit and HZ = 1000 > vif->credit_timeout->expire = 0xffffffff, vif->remaining_credit > = 0xffffffff, vif->credit_usec=0 jiffies=0 > vif receive lesser package (DomU send lesser package). If the > value is litter than 2K/s, consume 4G(0xffffffff) will need 582.55 > hours. jiffies will large than 0x7ffffff. we guess jiffies = > 0x800000ff, time_after_eq(0x800000ff, 0xffffffff) will failure, and > one time which expire is 0xfffffff will be pended into system. So > the interface will hung until jiffies recount 0xffffffff (that will > need very long time). If I'm not mistaken you meant time_after_eq(now, next_credit) in netback. How does next_credit become 0xffffffff? Wei. > > If some error exist in above explain, please help me point it out. > > Thanks, > Jason _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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