[TS-4844] Crash in HttpSM::state_cache_open_write

• Type: Bug
• Status: Open
• Priority: Blocker
• Resolution: Unresolved
• Fix Version/s: 7.1.0
• Component/s: HTTP
• Labels: A crash
• Assignee: Unassigned
• Reporter: Leif Hedstrom
• Created: 09/Sep/16 23:11
• Updated: 30/Sep/16 20:11

Description

We're seeing this crash, particularly (maybe even only) when we reload configurations on a running system:

#0  0x00002aaaaac8d08d in HttpSM::state_cache_open_write (this=0x2ae4964b4600, event=1109, data=0x2ae993968000) at HttpSM.cc:2503
#1  0x00002aaaaac9da9d in HttpSM::main_handler (this=0x2ae4964b4600, event=1109, data=0x2ae993968000) at HttpSM.cc:2661
#2  0x00002aaaaae8c650 in Continuation::handleEvent (data=0x2ae993968000, event=1109, this=<optimized out>) at I_Continuation.h:153
#3  EThread::process_event (this=0x2aaab3208000, e=0x2ae993968000, calling_code=1109) at UnixEThread.cc:148
#4  0x00002aaaaae8d47b in EThread::execute (this=0x2aaab3208000) at UnixEThread.cc:202
#5  0x00002aaaaae8c026 in spawn_thread_internal (a=0x2aaab0b25dc0) at Thread.cc:86
#6  0x00002aaaad6b3aa1 in start_thread (arg=0x2aaab480f700) at pthread_create.c:301
#7  0x00002aaaae8bc93d in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:115

Discussed with amc about what this could be, looking at the code, it seems related to the "new" option proxy.config.http.cache.open_write_fail_action. We've started turning off this setting for now.

The root cause of the crash is

(gdb) p cache_sm.cache_read_vc
$1 = (CacheVConnection *) 0x0

I.e. we end up in the CACHE_EVENT_OPEN_READ case, falling through from CACHE_EVENT_OPEN_WRITE_FAILED (which is the value of event):

(gdb) p event
$2 = 1109