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From: "burnus at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug fortran/99529] New: libgfortran I/O: Data races related to new unit / new unit calls for I/O to strings Date: Wed, 10 Mar 2021 21:10:59 +0000 [thread overview] Message-ID: <bug-99529-4@http.gcc.gnu.org/bugzilla/> (raw) https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99529 Bug ID: 99529 Summary: libgfortran I/O: Data races related to new unit / new unit calls for I/O to strings Product: gcc Version: 11.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: fortran Assignee: unassigned at gcc dot gnu.org Reporter: burnus at gcc dot gnu.org CC: jvdelisle at gcc dot gnu.org Target Milestone: --- Reported at https://gcc.gnu.org/pipermail/fortran/2021-March/055795.html Using helgrind on a simple omp do loop with write to a character variable, I get some possible data races in libgfortran/io/unit.c. There global array newunits is allocated and possibly reallocated in "newunit_alloc". According to the lock outputs from helgrind I see that this routine is called even if output is into a character variable. Routine "newunit_alloc" uses a lock to avoid having several threads all over the place. But newunit_free also writes to newunits array. And this routine does not obtain a lock itself (see comment above newunit_free in unit.c) So in theory it can happen that newunit_alloc reallocated newunits, and newunit_free writes to it just at this time. As I also use 18 threads the initial size of 16 does not suffice and reallocation does probably indeed happen. Also access to newunit_lwi is not protected as well (and complained about by helgrind).
next reply other threads:[~2021-03-10 21:10 UTC|newest] Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-03-10 21:10 burnus at gcc dot gnu.org [this message] 2021-03-10 21:30 ` [Bug fortran/99529] " burnus at gcc dot gnu.org 2021-03-11 8:30 ` rguenth at gcc dot gnu.org 2021-03-11 8:52 ` mscfd at gmx dot net 2021-03-11 9:07 ` mscfd at gmx dot net 2021-03-11 9:31 ` burnus at gcc dot gnu.org 2021-03-11 9:48 ` burnus at gcc dot gnu.org 2021-03-15 13:29 ` burnus at gcc dot gnu.org
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