From owner-svn-src-all@FreeBSD.ORG Tue Apr 24 17:51:37 2012 Return-Path: Delivered-To: svn-src-all@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [69.147.83.52]) by hub.freebsd.org (Postfix) with ESMTP id 0A4431065670; Tue, 24 Apr 2012 17:51:37 +0000 (UTC) (envelope-from kib@FreeBSD.org) Received: from svn.freebsd.org (svn.freebsd.org [IPv6:2001:4f8:fff6::2c]) by mx1.freebsd.org (Postfix) with ESMTP id E95318FC1C; Tue, 24 Apr 2012 17:51:36 +0000 (UTC) Received: from svn.freebsd.org (localhost [127.0.0.1]) by svn.freebsd.org (8.14.4/8.14.4) with ESMTP id q3OHpa2q058688; Tue, 24 Apr 2012 17:51:36 GMT (envelope-from kib@svn.freebsd.org) Received: (from kib@localhost) by svn.freebsd.org (8.14.4/8.14.4/Submit) id q3OHpaih058684; Tue, 24 Apr 2012 17:51:36 GMT (envelope-from kib@svn.freebsd.org) Message-Id: <201204241751.q3OHpaih058684@svn.freebsd.org> From: Konstantin Belousov Date: Tue, 24 Apr 2012 17:51:36 +0000 (UTC) To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org X-SVN-Group: head MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Cc: Subject: svn commit: r234657 - in head/lib/libc: include stdio X-BeenThere: svn-src-all@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: "SVN commit messages for the entire src tree \(except for " user" and " projects" \)" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 24 Apr 2012 17:51:37 -0000 Author: kib Date: Tue Apr 24 17:51:36 2012 New Revision: 234657 URL: http://svn.freebsd.org/changeset/base/234657 Log: Take the spinlock around clearing of the fp->_flags in fclose(3), which indicates the avaliability of FILE, to prevent possible reordering of the writes as seen by other CPUs. Reported by: Fengwei yin Reviewed by: jhb MFC after: 1 week Modified: head/lib/libc/include/libc_private.h head/lib/libc/stdio/fclose.c head/lib/libc/stdio/findfp.c Modified: head/lib/libc/include/libc_private.h ============================================================================== --- head/lib/libc/include/libc_private.h Tue Apr 24 17:00:30 2012 (r234656) +++ head/lib/libc/include/libc_private.h Tue Apr 24 17:51:36 2012 (r234657) @@ -81,6 +81,19 @@ void _rtld_error(const char *fmt, ...); #define FLOCKFILE(fp) if (__isthreaded) _FLOCKFILE(fp) #define FUNLOCKFILE(fp) if (__isthreaded) _funlockfile(fp) +struct _spinlock; +extern struct _spinlock __stdio_thread_lock; +#define STDIO_THREAD_LOCK() \ +do { \ + if (__isthreaded) \ + _SPINLOCK(&__stdio_thread_lock); \ +} while (0) +#define STDIO_THREAD_UNLOCK() \ +do { \ + if (__isthreaded) \ + _SPINUNLOCK(&__stdio_thread_lock); \ +} while (0) + /* * Indexes into the pthread jump table. * Modified: head/lib/libc/stdio/fclose.c ============================================================================== --- head/lib/libc/stdio/fclose.c Tue Apr 24 17:00:30 2012 (r234656) +++ head/lib/libc/stdio/fclose.c Tue Apr 24 17:51:36 2012 (r234657) @@ -41,6 +41,7 @@ __FBSDID("$FreeBSD$"); #include #include #include "un-namespace.h" +#include #include "libc_private.h" #include "local.h" @@ -65,7 +66,20 @@ fclose(FILE *fp) FREELB(fp); fp->_file = -1; fp->_r = fp->_w = 0; /* Mess up if reaccessed. */ + + /* + * Lock the spinlock used to protect __sglue list walk in + * __sfp(). The __sfp() uses fp->_flags == 0 test as an + * indication of the unused FILE. + * + * Taking the lock prevents possible compiler or processor + * reordering of the writes performed before the final _flags + * cleanup, making sure that we are done with the FILE before + * it is considered available. + */ + STDIO_THREAD_LOCK(); fp->_flags = 0; /* Release this FILE for reuse. */ + STDIO_THREAD_UNLOCK(); FUNLOCKFILE(fp); return (r); } Modified: head/lib/libc/stdio/findfp.c ============================================================================== --- head/lib/libc/stdio/findfp.c Tue Apr 24 17:00:30 2012 (r234656) +++ head/lib/libc/stdio/findfp.c Tue Apr 24 17:51:36 2012 (r234657) @@ -82,9 +82,7 @@ static struct glue *lastglue = &uglue; static struct glue * moreglue(int); -static spinlock_t thread_lock = _SPINLOCK_INITIALIZER; -#define THREAD_LOCK() if (__isthreaded) _SPINLOCK(&thread_lock) -#define THREAD_UNLOCK() if (__isthreaded) _SPINUNLOCK(&thread_lock) +spinlock_t __stdio_thread_lock = _SPINLOCK_INITIALIZER; #if NOT_YET #define SET_GLUE_PTR(ptr, val) atomic_set_rel_ptr(&(ptr), (uintptr_t)(val)) @@ -127,22 +125,22 @@ __sfp() /* * The list must be locked because a FILE may be updated. */ - THREAD_LOCK(); + STDIO_THREAD_LOCK(); for (g = &__sglue; g != NULL; g = g->next) { for (fp = g->iobs, n = g->niobs; --n >= 0; fp++) if (fp->_flags == 0) goto found; } - THREAD_UNLOCK(); /* don't hold lock while malloc()ing. */ + STDIO_THREAD_UNLOCK(); /* don't hold lock while malloc()ing. */ if ((g = moreglue(NDYNAMIC)) == NULL) return (NULL); - THREAD_LOCK(); /* reacquire the lock */ + STDIO_THREAD_LOCK(); /* reacquire the lock */ SET_GLUE_PTR(lastglue->next, g); /* atomically append glue to list */ lastglue = g; /* not atomic; only accessed when locked */ fp = g->iobs; found: fp->_flags = 1; /* reserve this slot; caller sets real flags */ - THREAD_UNLOCK(); + STDIO_THREAD_UNLOCK(); fp->_p = NULL; /* no current pointer */ fp->_w = 0; /* nothing to read or write */ fp->_r = 0; @@ -183,10 +181,10 @@ f_prealloc(void) for (g = &__sglue; (n -= g->niobs) > 0 && g->next; g = g->next) /* void */; if ((n > 0) && ((g = moreglue(n)) != NULL)) { - THREAD_LOCK(); + STDIO_THREAD_LOCK(); SET_GLUE_PTR(lastglue->next, g); lastglue = g; - THREAD_UNLOCK(); + STDIO_THREAD_UNLOCK(); } }