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  1. 05 Jun, 2010 9 commits
    • Linus Torvalds's avatar
      Merge git://git.kernel.org/pub/scm/linux/kernel/git/rusty/linux-2.6-for-linus · 90ec7819
      Linus Torvalds authored 
      * git://git.kernel.org/pub/scm/linux/kernel/git/rusty/linux-2.6-for-linus:
  module: fix bne2 "gave up waiting for init of module libcrc32c"
  module: verify_export_symbols under the lock
  module: move find_module check to end
  module: make locking more fine-grained.
  module: Make module sysfs functions private.
  module: move sysfs exposure to end of load_module
  module: fix kdb's illicit use of struct module_use.
  module: Make the 'usage' lists be two-way
      90ec7819
    • Rusty Russell's avatar
      module: fix bne2 "gave up waiting for init of module libcrc32c" · 9bea7f23
      Rusty Russell authored 
      Problem: it's hard to avoid an init routine stumbling over a
request_module these days.  And it's not clear it's always a bad idea:
for example, a module like kvm with dynamic dependencies on kvm-intel
or kvm-amd would be neater if it could simply request_module the right
one.

In this particular case, it's libcrc32c:

	libcrc32c_mod_init
	 crypto_alloc_shash
	  crypto_alloc_tfm
	   crypto_find_alg
	    crypto_alg_mod_lookup
	     crypto_larval_lookup
	      request_module

If another module is waiting inside resolve_symbol() for libcrc32c to
finish initializing (ie. bne2 depends on libcrc32c) then it does so
holding the module lock, and our request_module() can't make progress
until that is released.

Waiting inside resolve_symbol() without the lock isn't all that hard:
we just need to pass the -EBUSY up the call chain so we can sleep
where we don't hold the lock.  Error reporting is a bit trickier: we
need to copy the name of the unfinished module before releasing the
lock.

Other notes:
1) This also fixes a theoretical issue where a weak dependency would allow
   symbol version mismatches to be ignored.
2) We rename use_module to ref_module to make life easier for the only
   external user (the out-of-tree ksplice patches).
Signed-off-by: default avatarRusty Russell <rusty@rustcorp.com.au>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Tim Abbot <tabbott@ksplice.com>
Tested-by: default avatarBrandon Philips <bphilips@suse.de>
      9bea7f23
    • Rusty Russell's avatar
      module: verify_export_symbols under the lock · be593f4c
      Rusty Russell authored 
      It disabled preempt so it was "safe", but nothing stops another module
slipping in before this module is added to the global list now we don't
hold the lock the whole time.

So we check this just after we check for duplicate modules, and just
before we put the module in the global list.

(find_symbol finds symbols in coming and going modules, too).
Signed-off-by: default avatarRusty Russell <rusty@rustcorp.com.au>
      be593f4c
    • Linus Torvalds's avatar
      module: move find_module check to end · 3bafeb62
      Linus Torvalds authored 
      I think Rusty may have made the lock a bit _too_ finegrained there, and
didn't add it to some places that needed it. It looks, for example, like
PATCH 1/2 actually drops the lock in places where it's needed
("find_module()" is documented to need it, but now load_module() didn't
hold it at all when it did the find_module()).

Rather than adding a new "module_loading" list, I think we should be able
to just use the existing "modules" list, and just fix up the locking a
bit.

In fact, maybe we could just move the "look up existing module" a bit
later - optimistically assuming that the module doesn't exist, and then
just undoing the work if it turns out that we were wrong, just before
adding ourselves to the list.
Signed-off-by: default avatarRusty Russell <rusty@rustcorp.com.au>
      3bafeb62
    • Rusty Russell's avatar
      module: make locking more fine-grained. · 75676500
      Rusty Russell authored 
      Kay Sievers <kay.sievers@vrfy.org> reports that we still have some
contention over module loading which is slowing boot.

Linus also disliked a previous "drop lock and regrab" patch to fix the
bne2 "gave up waiting for init of module libcrc32c" message.

This is more ambitious: we only grab the lock where we need it.
Signed-off-by: default avatarRusty Russell <rusty@rustcorp.com.au>
Cc: Brandon Philips <brandon@ifup.org>
Cc: Kay Sievers <kay.sievers@vrfy.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
      75676500
    • Rusty Russell's avatar
      module: Make module sysfs functions private. · 6407ebb2
      Rusty Russell authored 
      These were placed in the header in ef665c1a to get the various
SYSFS/MODULE config combintations to compile.

That may have been necessary then, but it's not now.  These functions
are all local to module.c.
Signed-off-by: default avatarRusty Russell <rusty@rustcorp.com.au>
Cc: Randy Dunlap <randy.dunlap@oracle.com>
      6407ebb2
    • Rusty Russell's avatar
      module: move sysfs exposure to end of load_module · 80a3d1bb
      Rusty Russell authored 
      This means a little extra work, but is more logical: we don't put
anything in sysfs until we're about to put the module into the
global list an parse its parameters.

This also gives us a logical place to put duplicate module detection
in the next patch.
Signed-off-by: default avatarRusty Russell <rusty@rustcorp.com.au>
      80a3d1bb
    • Rusty Russell's avatar
      module: fix kdb's illicit use of struct module_use. · c8e21ced
      Rusty Russell authored 
      Linus changed the structure, and luckily this didn't compile any more.
Reported-by: default avatarStephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: default avatarRusty Russell <rusty@rustcorp.com.au>
Cc: Jason Wessel <jason.wessel@windriver.com>
Cc: Martin Hicks <mort@sgi.com>
      c8e21ced
    • Linus Torvalds's avatar
      module: Make the 'usage' lists be two-way · 2c02dfe7
      Linus Torvalds authored 
      When adding a module that depends on another one, we used to create a
one-way list of "modules_which_use_me", so that module unloading could
see who needs a module.

It's actually quite simple to make that list go both ways: so that we
not only can see "who uses me", but also see a list of modules that are
"used by me".

In fact, we always wanted that list in "module_unload_free()": when we
unload a module, we want to also release all the other modules that are
used by that module.  But because we didn't have that list, we used to
first iterate over all modules, and then iterate over each "used by me"
list of that module.

By making the list two-way, we simplify module_unload_free(), and it
allows for some trivial fixes later too.
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> (cleaned & rebased)
      2c02dfe7
  3. 04 Jun, 2010 31 commits
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