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Date:      Mon, 08 Jun 2015 14:04:45 -0400
From:      John Baldwin <jhb@freebsd.org>
To:        Ruslan Bukin <br@freebsd.org>
Cc:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   Re: svn commit: r284153 - head/sys/kern
Message-ID:  <1554833.IUNnl2bGYK@ralph.baldwin.cx>
In-Reply-To: <20150608144629.GA37834@bsdpad.com>
References:  <201506081406.t58E6mvA033492@svn.freebsd.org> <20150608144629.GA37834@bsdpad.com>

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On Monday, June 08, 2015 03:46:29 PM Ruslan Bukin wrote:
> For some reason it hangs for me after 'random' lines on arm64

Are you using dtrace?  It looks like sdt was using the public symbol before
but in a context where the caller held the lock.  I will revert this for now.
I think I can perhaps make it 'automatic' by having it acquire a read lock
(possibly recursing) if it doesn't already hold a write lock.

> FreeBSD clang version 3.6.1 (tags/RELEASE_361/final 237755) 20150525
> CPU: ARM Cortex-A57 r1p0
> IMPLEMENT ME: dtrace_toxic_ranges
> random: entropy device infrastructure driver
> random: selecting highest priority adaptor <Dummy>
> 
> On Mon, Jun 08, 2015 at 02:06:48PM +0000, John Baldwin wrote:
> > Author: jhb
> > Date: Mon Jun  8 14:06:47 2015
> > New Revision: 284153
> > URL: https://svnweb.freebsd.org/changeset/base/284153
> > 
> > Log:
> >   Add an internal "locked" variant of linker_file_lookup_set() and change
> >   the public function to acquire the global linker lock directly.  This
> >   permits linker_file_lookup_set() to be safely used from other modules.
> > 
> > Modified:
> >   head/sys/kern/kern_linker.c
> > 
> > Modified: head/sys/kern/kern_linker.c
> > ==============================================================================
> > --- head/sys/kern/kern_linker.c	Mon Jun  8 13:23:56 2015	(r284152)
> > +++ head/sys/kern/kern_linker.c	Mon Jun  8 14:06:47 2015	(r284153)
> > @@ -137,6 +137,8 @@ static int	linker_file_add_dependency(li
> >  		    linker_file_t dep);
> >  static caddr_t	linker_file_lookup_symbol_internal(linker_file_t file,
> >  		    const char* name, int deps);
> > +static int	linker_file_lookup_set_locked(linker_file_t file,
> > +		    const char *name, void *firstp, void *lastp, int *countp);
> >  static int	linker_load_module(const char *kldname,
> >  		    const char *modname, struct linker_file *parent,
> >  		    const struct mod_depend *verinfo, struct linker_file **lfpp);
> > @@ -189,7 +191,8 @@ linker_file_sysinit(linker_file_t lf)
> >  
> >  	sx_assert(&kld_sx, SA_XLOCKED);
> >  
> > -	if (linker_file_lookup_set(lf, "sysinit_set", &start, &stop, NULL) != 0)
> > +	if (linker_file_lookup_set_locked(lf, "sysinit_set", &start, &stop,
> > +	    NULL) != 0)
> >  		return;
> >  	/*
> >  	 * Perform a bubble sort of the system initialization objects by
> > @@ -237,7 +240,7 @@ linker_file_sysuninit(linker_file_t lf)
> >  
> >  	sx_assert(&kld_sx, SA_XLOCKED);
> >  
> > -	if (linker_file_lookup_set(lf, "sysuninit_set", &start, &stop,
> > +	if (linker_file_lookup_set_locked(lf, "sysuninit_set", &start, &stop,
> >  	    NULL) != 0)
> >  		return;
> >  
> > @@ -288,7 +291,8 @@ linker_file_register_sysctls(linker_file
> >  
> >  	sx_assert(&kld_sx, SA_XLOCKED);
> >  
> > -	if (linker_file_lookup_set(lf, "sysctl_set", &start, &stop, NULL) != 0)
> > +	if (linker_file_lookup_set_locked(lf, "sysctl_set", &start, &stop,
> > +	    NULL) != 0)
> >  		return;
> >  
> >  	sx_xunlock(&kld_sx);
> > @@ -309,7 +313,8 @@ linker_file_unregister_sysctls(linker_fi
> >  
> >  	sx_assert(&kld_sx, SA_XLOCKED);
> >  
> > -	if (linker_file_lookup_set(lf, "sysctl_set", &start, &stop, NULL) != 0)
> > +	if (linker_file_lookup_set_locked(lf, "sysctl_set", &start, &stop,
> > +	    NULL) != 0)
> >  		return;
> >  
> >  	sx_xunlock(&kld_sx);
> > @@ -332,7 +337,7 @@ linker_file_register_modules(linker_file
> >  
> >  	sx_assert(&kld_sx, SA_XLOCKED);
> >  
> > -	if (linker_file_lookup_set(lf, "modmetadata_set", &start,
> > +	if (linker_file_lookup_set_locked(lf, "modmetadata_set", &start,
> >  	    &stop, NULL) != 0) {
> >  		/*
> >  		 * This fallback should be unnecessary, but if we get booted
> > @@ -742,8 +747,8 @@ linker_file_add_dependency(linker_file_t
> >   * This function is used in this file so we can avoid having lots of (void **)
> >   * casts.
> >   */
> > -int
> > -linker_file_lookup_set(linker_file_t file, const char *name,
> > +static int
> > +linker_file_lookup_set_locked(linker_file_t file, const char *name,
> >      void *firstp, void *lastp, int *countp)
> >  {
> >  
> > @@ -751,6 +756,19 @@ linker_file_lookup_set(linker_file_t fil
> >  	return (LINKER_LOOKUP_SET(file, name, firstp, lastp, countp));
> >  }
> >  
> > +int
> > +linker_file_lookup_set(linker_file_t file, const char *name,
> > +    void *firstp, void *lastp, int *countp)
> > +{
> > +	int error;
> > +
> > +	sx_slock(&kld_sx);
> > +	error = linker_file_lookup_set_locked(file, name, firstp, lastp,
> > +	    countp);
> > +	sx_sunlock(&kld_sx);
> > +	return (error);
> > +}
> > +
> >  /*
> >   * List all functions in a file.
> >   */
> > @@ -1469,8 +1487,8 @@ linker_preload(void *arg)
> >  	/*
> >  	 * First get a list of stuff in the kernel.
> >  	 */
> > -	if (linker_file_lookup_set(linker_kernel_file, MDT_SETNAME, &start,
> > -	    &stop, NULL) == 0)
> > +	if (linker_file_lookup_set_locked(linker_kernel_file, MDT_SETNAME,
> > +	    &start, &stop, NULL) == 0)
> >  		linker_addmodules(linker_kernel_file, start, stop, 1);
> >  
> >  	/*
> > @@ -1479,7 +1497,7 @@ linker_preload(void *arg)
> >  	 */
> >  restart:
> >  	TAILQ_FOREACH(lf, &loaded_files, loaded) {
> > -		error = linker_file_lookup_set(lf, MDT_SETNAME, &start,
> > +		error = linker_file_lookup_set_locked(lf, MDT_SETNAME, &start,
> >  		    &stop, NULL);
> >  		/*
> >  		 * First, look to see if we would successfully link with this
> > @@ -1573,7 +1591,7 @@ restart:
> >  				panic("cannot add dependency");
> >  		}
> >  		lf->userrefs++;	/* so we can (try to) kldunload it */
> > -		error = linker_file_lookup_set(lf, MDT_SETNAME, &start,
> > +		error = linker_file_lookup_set_locked(lf, MDT_SETNAME, &start,
> >  		    &stop, NULL);
> >  		if (!error) {
> >  			for (mdp = start; mdp < stop; mdp++) {
> > @@ -1610,7 +1628,7 @@ restart:
> >  			goto fail;
> >  		}
> >  		linker_file_register_modules(lf);
> > -		if (linker_file_lookup_set(lf, "sysinit_set", &si_start,
> > +		if (linker_file_lookup_set_locked(lf, "sysinit_set", &si_start,
> >  		    &si_stop, NULL) == 0)
> >  			sysinit_add(si_start, si_stop);
> >  		linker_file_register_sysctls(lf);
> > @@ -2042,7 +2060,7 @@ linker_load_dependencies(linker_file_t l
> >  		if (error)
> >  			return (error);
> >  	}
> > -	if (linker_file_lookup_set(lf, MDT_SETNAME, &start, &stop,
> > +	if (linker_file_lookup_set_locked(lf, MDT_SETNAME, &start, &stop,
> >  	    &count) != 0)
> >  		return (0);
> >  	for (mdp = start; mdp < stop; mdp++) {
> > 
> 


-- 
John Baldwin



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