Date: Tue, 12 Jan 2021 11:16:25 +0000 From: Alexander Richardson <arichardson@freebsd.org> To: Konstantin Belousov <kib@freebsd.org> Cc: src-committers <src-committers@freebsd.org>, dev-commits-src-all@freebsd.org, dev-commits-src-main@freebsd.org Subject: Re: git: 85d028223bc2 - main - libthr malloc: support recursion on thr_malloc_umtx. Message-ID: <CA%2BZ_v8qh6%2BP5x88ziXQS3q90%2BG-gFTDVgO%2B7bV3RmGYakLVkDw@mail.gmail.com> In-Reply-To: <202101121046.10CAkLxI018198@gitrepo.freebsd.org> References: <202101121046.10CAkLxI018198@gitrepo.freebsd.org>
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On Tue, 12 Jan 2021 at 10:46, Konstantin Belousov <kib@freebsd.org> wrote: > > The branch main has been updated by kib: > > URL: https://cgit.FreeBSD.org/src/commit/?id=85d028223bc2768651f4d44881644ceb5dc2a664 > > commit 85d028223bc2768651f4d44881644ceb5dc2a664 > Author: Konstantin Belousov <kib@FreeBSD.org> > AuthorDate: 2021-01-12 09:02:37 +0000 > Commit: Konstantin Belousov <kib@FreeBSD.org> > CommitDate: 2021-01-12 10:45:44 +0000 > > libthr malloc: support recursion on thr_malloc_umtx. > > One possible way the recursion can happen is during fork: suppose > that fork is called from early code that did not triggered > jemalloc(3) initialization yet. Then we lock thr_malloc lock, and > call malloc_prefork() that might require initialization of jemalloc > pthread_mutexes, calling into libthr malloc. It is safe to allow > recursion for this occurence. > > PR: 252579 > Reported by: Vasily Postnicov <shamaz.mazum@gmail.com> > MFC after: 1 week > Sponsored by: The FreeBSD Foundation > --- > lib/libthr/thread/thr_malloc.c | 13 +++++++++++-- > 1 file changed, 11 insertions(+), 2 deletions(-) > > diff --git a/lib/libthr/thread/thr_malloc.c b/lib/libthr/thread/thr_malloc.c > index 2f1c81142942..80a81f9c6c27 100644 > --- a/lib/libthr/thread/thr_malloc.c > +++ b/lib/libthr/thread/thr_malloc.c > @@ -41,6 +41,7 @@ int npagesizes; > size_t *pagesizes; > static size_t pagesizes_d[2]; > static struct umutex thr_malloc_umtx; > +static u_int thr_malloc_umtx_level; > > void > __thr_malloc_init(void) > @@ -60,11 +61,16 @@ __thr_malloc_init(void) > static void > thr_malloc_lock(struct pthread *curthread) > { > + uint32_t curtid; > > if (curthread == NULL) > return; > curthread->locklevel++; > - _thr_umutex_lock(&thr_malloc_umtx, TID(curthread)); > + curtid = TID(curthread); > + if ((uint32_t)thr_malloc_umtx.m_owner == curtid) > + thr_malloc_umtx_level++; > + else > + _thr_umutex_lock(&thr_malloc_umtx, curtid); > } > > static void > @@ -73,7 +79,10 @@ thr_malloc_unlock(struct pthread *curthread) > > if (curthread == NULL) > return; > - _thr_umutex_unlock(&thr_malloc_umtx, TID(curthread)); > + if (thr_malloc_umtx_level > 0) > + thr_malloc_umtx_level--; Should this also assert that "thr_malloc_umtx.m_owner == curtid"? Thanks, Alex > + else > + _thr_umutex_unlock(&thr_malloc_umtx, TID(curthread)); > curthread->locklevel--; > _thr_ast(curthread); > }
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