Date: Tue, 12 May 2015 02:08:54 +0000 From: bugzilla-noreply@freebsd.org To: freebsd-threads@FreeBSD.org Subject: [Bug 200138] [PATCH] Fixed race condition incurred in libthr by some foreign malloc libraries Message-ID: <bug-200138-16@https.bugs.freebsd.org/bugzilla/>
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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=200138 Bug ID: 200138 Summary: [PATCH] Fixed race condition incurred in libthr by some foreign malloc libraries Product: Base System Version: 10.1-STABLE Hardware: Any OS: Any Status: New Keywords: patch Severity: Affects Only Me Priority: --- Component: threads Assignee: freebsd-threads@FreeBSD.org Reporter: yuri@rawbw.com Keywords: patch Created attachment 156674 --> https://bugs.freebsd.org/bugzilla/attachment.cgi?id=156674&action=edit patch While investigating the message coming from "Thread %p has exited with %d leftover", I found that _pthread_setspecific is entered twice with the same TCB, _get_curthread() returned the same thread pointer. Second invocation was incurred by the google tcmalloc library (devel/google-perftools port). > (gdb) bt > #0 yuri_enter (serno=60) at /usr/src/lib/libthr/thread/thr_spec.c:60 > #1 0x0000000804e23e89 in _pthread_setspecific (userkey=3, value=0x740a080) at /usr/src/lib/libthr/thread/thr_spec.c:228 > #2 0x000000080408b95c in ?? () from /usr/local/lib/qt4/libQtCore.so.4 > #3 0x0000000804e1da3a in thread_start (curthread=0x73f6800) at /usr/src/lib/libthr/thread/thr_create.c:288 > #4 0x0000000000000000 in ?? () > Backtrace stopped: Cannot access memory at address 0x7fffdf9fb000 > (gdb) bt > #0 yuri_enter (serno=61) at /usr/src/lib/libthr/thread/thr_spec.c:60 > #1 0x0000000804e23e89 in _pthread_setspecific (userkey=2, value=0x7a9520) at /usr/src/lib/libthr/thread/thr_spec.c:228 > #2 0x00000008008ff4de in perftools_pthread_setspecific(int, void*) () from /usr/local/lib/libtcmalloc.so.4 > #3 0x00000008008f2322 in tcmalloc::ThreadCache::CreateCacheIfNecessary() () from /usr/local/lib/libtcmalloc.so.4 > #4 0x00000008008ea666 in ?? () from /usr/local/lib/libtcmalloc.so.4 > #5 0x00000008008ffd92 in tc_calloc () from /usr/local/lib/libtcmalloc.so.4 > #6 0x0000000804e243a1 in pthread_key_allocate_data () at /usr/src/lib/libthr/thread/thr_spec.c:212 > #7 0x0000000804e23f19 in _pthread_setspecific (userkey=3, value=0x740a080) at /usr/src/lib/libthr/thread/thr_spec.c:231 > #8 0x000000080408b95c in ?? () from /usr/local/lib/qt4/libQtCore.so.4 > #9 0x0000000804e1da3a in thread_start (curthread=0x73f6800) at /usr/src/lib/libthr/thread/thr_create.c:288 > #10 0x0000000000000000 in ?? () This causes some memory loss, and stray message about leftover TLS data. The attached patch corrects for such potential problem by double-checking the pthread's "specific" array after allocating it, and frees the newly allocated copy if it happens to be already allocated. Please keep the comment, because I think these lines may appear very confusing and wrong to people without the knowledge of this specific situation. -- You are receiving this mail because: You are the assignee for the bug.
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