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Commit cb618965 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge git://git.kernel.org/pub/scm/linux/kernel/git/rusty/linux-2.6-for-linus 

* git://git.kernel.org/pub/scm/linux/kernel/git/rusty/linux-2.6-for-linus:
  stop_machine: make stop_machine_run more virtualization friendly
  doc: add a chapter about trylock functions [Bug 9011]
  modules: proper cleanup of kobject without CONFIG_SYSFS
  module loading ELF handling: use SELFMAG instead of numeric constant
parents 5e2daeb3 3401a61e

Documentation/DocBook/kernel-locking.tmpl

+25 −0
Original line number Diff line number Diff line
@@ -703,6 +703,31 @@ 
</sect1>

</chapter>



<chapter id="trylock-functions">

 <title>The trylock Functions</title>

  <para>

   There are functions that try to acquire a lock only once and immediately

   return a value telling about success or failure to acquire the lock.

   They can be used if you need no access to the data protected with the lock

   when some other thread is holding the lock. You should acquire the lock

   later if you then need access to the data protected with the lock.

  </para>



  <para>

    <function>spin_trylock()</function> does not spin but returns non-zero if

    it acquires the spinlock on the first try or 0 if not. This function can

    be used in all contexts like <function>spin_lock</function>: you must have

    disabled the contexts that might interrupt you and acquire the spin lock.

  </para>



  <para>

    <function>mutex_trylock()</function> does not suspend your task

    but returns non-zero if it could lock the mutex on the first try

    or 0 if not. This function cannot be safely used in hardware or software

    interrupt contexts despite not sleeping.

  </para>

</chapter>



  <chapter id="Examples">

   <title>Common Examples</title>

    <para>

kernel/module.c

+15 −3
Original line number Diff line number Diff line
@@ -1337,7 +1337,19 @@ int mod_sysfs_setup(struct module *mod, 
	kobject_put(&mod->mkobj.kobj);

	return err;

}

#endif



static void mod_sysfs_fini(struct module *mod)

{

	kobject_put(&mod->mkobj.kobj);

}



#else /* CONFIG_SYSFS */



static void mod_sysfs_fini(struct module *mod)

{

}



#endif /* CONFIG_SYSFS */



static void mod_kobject_remove(struct module *mod)

{
@@ -1345,7 +1357,7 @@ static void mod_kobject_remove(struct module *mod) 
	module_param_sysfs_remove(mod);

	kobject_put(mod->mkobj.drivers_dir);

	kobject_put(mod->holders_dir);

	kobject_put(&mod->mkobj.kobj);

	mod_sysfs_fini(mod);

}



/*
@@ -1780,7 +1792,7 @@ static struct module *load_module(void __user *umod, 


	/* Sanity checks against insmoding binaries or wrong arch,

           weird elf version */

	if (memcmp(hdr->e_ident, ELFMAG, 4) != 0

	if (memcmp(hdr->e_ident, ELFMAG, SELFMAG) != 0

	    || hdr->e_type != ET_REL

	    || !elf_check_arch(hdr)

	    || hdr->e_shentsize != sizeof(*sechdrs)) {

kernel/stop_machine.c

+4 −3
Original line number Diff line number Diff line
@@ -62,7 +62,6 @@ static int stopmachine(void *cpu) 
		 * help our sisters onto their CPUs. */

		if (!prepared && !irqs_disabled)

			yield();

		else

		cpu_relax();

	}
@@ -106,8 +105,10 @@ static int stop_machine(void) 
	}



	/* Wait for them all to come to life. */

	while (atomic_read(&stopmachine_thread_ack) != stopmachine_num_threads)

	while (atomic_read(&stopmachine_thread_ack) != stopmachine_num_threads) {

		yield();

		cpu_relax();

	}



	/* If some failed, kill them all. */

	if (ret < 0) {