On Mon, Nov 22, 2010 at 11:13:06AM +0100, Alexander Leidinger wrote: > Quoting Kostik Belousov <kostik...@gmail.com> (from Mon, 22 Nov 2010 > 11:31:34 +0200): > > >On Mon, Nov 22, 2010 at 09:07:00AM +0000, Alexander Leidinger wrote: > >>Author: netchild > >>Date: Mon Nov 22 09:06:59 2010 > >>New Revision: 215664 > >>URL: http://svn.freebsd.org/changeset/base/215664 > >> > >>Log: > >> By using the 32-bit Linux version of Sun's Java Development Kit 1.6 > >> on FreeBSD (amd64), invocations of "javac" (or "java") eventually > >> end with the output of "Killed" and exit code 137. > > > >>@@ -196,6 +198,12 @@ linux_proc_exit(void *arg __unused, stru > >> } else > >> EMUL_SHARED_WUNLOCK(&emul_shared_lock); > >> > >>+ if ((shared_flags & EMUL_SHARED_HASXSTAT) != 0) { > >>+ PROC_LOCK(p); > >>+ p->p_xstat = shared_xstat; > >>+ PROC_UNLOCK(p); > >>+ } > >Why is process lock taken there ? The assignment to u_short inside the > >properly aligned structure is atomic on all supported architectures, and > >the thread that should see side-effect of assignment is the same thread > >that does assignment. > > Change below. > > >>+ > >> if (child_clear_tid != NULL) { > >> struct linux_sys_futex_args cup; > >> int null = 0; > >>@@ -257,6 +265,9 @@ linux_proc_exec(void *arg __unused, stru > >> if (__predict_false(imgp->sysent == &elf_linux_sysvec > >> && p->p_sysent != &elf_linux_sysvec)) > >> linux_proc_init(FIRST_THREAD_IN_PROC(p), p->p_pid, 0); > >>+ if (__predict_false(p->p_sysent == &elf_linux_sysvec)) > >>+ /* Kill threads regardless of imgp->sysent value */ > >>+ linux_kill_threads(FIRST_THREAD_IN_PROC(p), SIGKILL); > >This is better expressed by > > if ((p->p_sysent->sv_flags & SV_ABI_MASK) == SV_ABI_LINUX) > > Is this OK for you? > ---snip--- > Index: compat/linux/linux_emul.c > =================================================================== > --- compat/linux/linux_emul.c (Revision 215664) > +++ compat/linux/linux_emul.c (Arbeitskopie) > @@ -198,11 +198,8 @@ > } else > EMUL_SHARED_WUNLOCK(&emul_shared_lock); > > - if ((shared_flags & EMUL_SHARED_HASXSTAT) != 0) { > - PROC_LOCK(p); > + if ((shared_flags & EMUL_SHARED_HASXSTAT) != 0) > p->p_xstat = shared_xstat; > - PROC_UNLOCK(p); > - } > > if (child_clear_tid != NULL) { > struct linux_sys_futex_args cup; > @@ -265,7 +262,8 @@ > if (__predict_false(imgp->sysent == &elf_linux_sysvec > && p->p_sysent != &elf_linux_sysvec)) > linux_proc_init(FIRST_THREAD_IN_PROC(p), p->p_pid, 0); > - if (__predict_false(p->p_sysent == &elf_linux_sysvec)) > + if (__predict_false((p->p_sysent->sv_flags & SV_ABI_MASK) == > + SV_ABI_LINUX)) > /* Kill threads regardless of imgp->sysent value */ > linux_kill_threads(FIRST_THREAD_IN_PROC(p), SIGKILL); > if (__predict_false(imgp->sysent != &elf_linux_sysvec > ---snip--- Yes.
> > >Regardless of this mostly cosmetic issue, this is racy. Other > >linux thread in the same process might do an execve(3). > >More, if execve(3) call fails, then you return into the process > >that lacks all threads except the one that called execve(3). > > How critical is this in your opinion (relative to the issue this patch > is fixing)? Do you prefer a backout or do you think the probability > that the someone wins the race is low enough? > > Do you see a solution for the race? I did not asked for backout, nor I am asking now. Most likely, the semantic of linux thread groups cannot be implemented by only using event handlers that linux.ko hooks now. How linux handles single-threading when doing execve(2) from multithreaded process ?
pgpIriIujbv2q.pgp
Description: PGP signature
