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https://issues.apache.org/jira/browse/TS-1240?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13274396#comment-13274396
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John Plevyak commented on TS-1240:
----------------------------------
I think removing the delay buffer before deleting the LogBuffer has lead to
this race condition. The problem is that checkout_write can execute at the
same time as the flush. The only thing that prevents a problem is that
checkout_write will fail when it finds that the buffer is full. When a buffer
becomes full there can still be other threads trying to do checkout_write, so
the buffer must not be deleted immediately after the flush... instead it is
kept around for a while, until all the other thread which might be doing
checkout_write figure out that the buffer is full and back out and reload the
current buffer pointer (which is going to be different). Once all those
threads have dropped references to the LogBuffer, it is finally OK to delete
it. This should probably be documented in grizzly detail in the LogObject
file. It is a bit of a pain, but it does make it possible to implement the
critical path of logging completely without locks.
Do you want me to generate a patch?
> Debug assert triggered in LogBuffer.cc:209
> ------------------------------------------
>
> Key: TS-1240
> URL: https://issues.apache.org/jira/browse/TS-1240
> Project: Traffic Server
> Issue Type: Bug
> Components: Logging
> Affects Versions: 3.1.4
> Reporter: Leif Hedstrom
> Fix For: 3.1.5
>
>
> From John:
> {code}
> [May 1 09:08:44.746] Server {0x7ffff7fce800} NOTE: traffic server running
> FATAL: LogBuffer.cc:209: failed assert `m_unaligned_buffer`
> /a/home/jplevyak/projects/ts/ts-2/proxy/.libs/lt-traffic_server - STACK
> TRACE:
> /home/jplevyak/projects/ts/ts-2/lib/ts/.libs/libtsutil.so.3(ink_fatal+0xa3)[0x7ffff7bae4a5]
> /home/jplevyak/projects/ts/ts-2/lib/ts/.libs/libtsutil.so.3(_ink_assert+0x3c)[0x7ffff7bad47c]
> /a/home/jplevyak/projects/ts/ts-2/proxy/.libs/lt-traffic_server(_ZN9LogBuffer14checkout_writeEPmm+0x35)[0x5d3a53]
> /a/home/jplevyak/projects/ts/ts-2/proxy/.libs/lt-traffic_server(_ZN9LogObject15_checkout_writeEPmm+0x41)[0x5eef75]
> /a/home/jplevyak/projects/ts/ts-2/proxy/.libs/lt-traffic_server(_ZN9LogObject3logEP9LogAccessPc+0x4cb)[0x5ef5b9]
> /a/home/jplevyak/projects/ts/ts-2/proxy/.libs/lt-traffic_server(_ZN16LogObjectManager3logEP9LogAccess+0x4a)[0x5daab4]
> /a/home/jplevyak/projects/ts/ts-2/proxy/.libs/lt-traffic_server(_ZN3Log6accessEP9LogAccess+0x235)[0x5d97f9]
> /a/home/jplevyak/projects/ts/ts-2/proxy/.libs/lt-traffic_server(_ZN6HttpSM12update_statsEv+0x204)[0x579872]
> /a/home/jplevyak/projects/ts/ts-2/proxy/.libs/lt-traffic_server(_ZN6HttpSM9kill_thisEv+0x31d)[0x579525]
> /a/home/jplevyak/projects/ts/ts-2/proxy/.libs/lt-traffic_server(_ZN6HttpSM12main_handlerEiPv+0x337)[0x56cec1]
> /a/home/jplevyak/projects/ts/ts-2/proxy/.libs/lt-traffic_server(_ZN12Continuation11handleEventEiPv+0x72)[0x4e2450]
> /a/home/jplevyak/projects/ts/ts-2/proxy/.libs/lt-traffic_server(_ZN10HttpTunnel12main_handlerEiPv+0x14c)[0x5b24aa]
> /a/home/jplevyak/projects/ts/ts-2/proxy/.libs/lt-traffic_server(_ZN12Continuation11handleEventEiPv+0x72)[0x4e2450]
> /a/home/jplevyak/projects/ts/ts-2/proxy/.libs/lt-traffic_server[0x6bb9d1]
> /a/home/jplevyak/projects/ts/ts-2/proxy/.libs/lt-traffic_server[0x6bbafa]
> /a/home/jplevyak/projects/ts/ts-2/proxy/.libs/lt-traffic_server(_Z15write_to_net_ioP10NetHandlerP18UnixNetVConnectionP7EThread+0x6fa)[0x6bcaaf]
> /a/home/jplevyak/projects/ts/ts-2/proxy/.libs/lt-traffic_server(_Z12write_to_netP10NetHandlerP18UnixNetVConnectionP14PollDescriptorP7EThread+0x7d)[0x6bc3b3]
> /a/home/jplevyak/projects/ts/ts-2/proxy/.libs/lt-traffic_server(_ZN10NetHandler12mainNetEventEiP5Event+0x6e6)[0x6b8828]
> /a/home/jplevyak/projects/ts/ts-2/proxy/.libs/lt-traffic_server(_ZN12Continuation11handleEventEiPv+0x72)[0x4e2450]
> /a/home/jplevyak/projects/ts/ts-2/proxy/.libs/lt-traffic_server(_ZN7EThread13process_eventEP5Eventi+0x111)[0x6dde7f]
> /a/home/jplevyak/projects/ts/ts-2/proxy/.libs/lt-traffic_server(_ZN7EThread7executeEv+0x431)[0x6de42b]
> /a/home/jplevyak/projects/ts/ts-2/proxy/.libs/lt-traffic_server[0x6dd0bc]
> /lib64/libpthread.so.0(+0x7d90)[0x7ffff7676d90]
> /lib64/libc.so.6(clone+0x6d)[0x7ffff54f9f5d]
> {code}
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