Date: Sun, 17 Apr 2011 11:21:07 -0400 (EDT) From: Daniel Eischen <eischen@vigrid.com> To: Andriy Gapon <avg@freebsd.org> Cc: hackers@freebsd.org, freebsd-threads@freebsd.org Subject: Re: puzzled: fork +libthr Message-ID: <Pine.GSO.4.64.1104171119110.5365@sea.ntplx.net> In-Reply-To: <4DAAFBAF.90700@FreeBSD.org> References: <4DA98197.8060104@FreeBSD.org> <4DAAFBAF.90700@FreeBSD.org>
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On Sun, 17 Apr 2011, Andriy Gapon wrote: > on 16/04/2011 14:46 Andriy Gapon said the following: >> The second puzzle is the EPERM return value itself, on stable/8. >> From what I seem chromium does a bunch of forks before it gets to the place of >> interest. My debugging shows that those forks are "single-threaded" (i.e. code >> in thr_fork.c is not called). And then in a process/thread that makes that >> pthread_cond_wait call I see that libthr and kernel have different opinions >> about what current TID is. Userland part uses what is actually a kernel TID of >> its parent thread (the one that called fork). And given how the work is divided >> between userland and kernel in libthr, that mismatch leads to serious consequences. >> >> So my question is why libthr doesn't see its actual TID. Maybe some >> initialization code is not invoked. BTW, chromium is linked to both libc and >> libthr (per ldd). But it seems that there are no pthread calls up the fork >> chain until that pthread_cond_wait call. > > The second problem seems to be caused by chrome binary being linked to libc and > libthr in "incorrect order", libc comes before libthr in ldd output. My > debugging shows that fork is resolved from libc, not from libthr. > Not sure what to blame here: > - build toolchain for putting libc before libthr > - rtld for not preferring libthr over libc > - libc/libthr for being split into two pieces in the current way - The build procedure for chromium. libc/[libc_r, libpthread, libthr] have always behaved that way since the libc/libc_r split. -- DE
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