At Wed, 26 Feb 2014 14:22:21 +0900, FUJITA Tomonori wrote: > > On Wed, 26 Feb 2014 14:13:22 +0900 > Hitoshi Mitake <mitake.hitoshi@xxxxxxxxxxxxx> wrote: > > > Current main event loop (event_loop()) of tgtd has a possibility of > > segmentation fault. The problem is caused by the below sequence: > > > > 1. Event A, B are ready so epoll_wait(2) returns. > > 2. The handler of the event A is called. In the event handler, the > > event B is deleted with tgt_event_del() > > 3. event_loop() tries to call the handler of the event B. It causes > > segfault because the event struct is already removed and freed. > > > > For avoid this problem, this patch adds a new global variable > > event_need_refresh. If the value of this variable is 1, event_loop() > > calls epoll_wait(2) again for refreshing ready fd list. This patch > > also lets tgt_event_del() to turn on the flag in its tail. > > > > For example, we can produce segfault of tgtd under heavy load. Below > > is a backtrace obtained from the core file: > > (gdb) bt > > #0 0x0000000000000000 in ?? () > > #1 0x0000000000411419 in event_loop () at tgtd.c:414 > > #2 0x0000000000411b65 in main (argc=<value optimized out>, argv=<value optimized out>) at tgtd.c:591 > > > > To be honest, I still don't find an event handler which calls > > tgt_event_del() for other fds. But with this modification, the above > > segfault is avoided. The change seems to be effective. > > As you pointed out off-line, making a connection closed via tgtadm > might be the case. Anyway, I think that the handler API should allow > removing other handlers from a handler. Merged, thanks a lot! > > > +int event_need_refresh; > > + > > static? Ah, the variable should be static one. I'll send a patch later. Thanks, Hitoshi -- To unsubscribe from this list: send the line "unsubscribe stgt" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
