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  1. 03 Feb, 2022 5 commits
    • Igor Pylypiv's avatar
      Revert "module, async: async_synchronize_full() on module init iff async is used" · 67d6212a
      Igor Pylypiv authored 
      This reverts commit 774a1221.

We need to finish all async code before the module init sequence is
done.  In the reverted commit the PF_USED_ASYNC flag was added to mark a
thread that called async_schedule().  Then the PF_USED_ASYNC flag was
used to determine whether or not async_synchronize_full() needs to be
invoked.  This works when modprobe thread is calling async_schedule(),
but it does not work if module dispatches init code to a worker thread
which then calls async_schedule().

For example, PCI driver probing is invoked from a worker thread based on
a node where device is attached:

	if (cpu < nr_cpu_ids)
		error = work_on_cpu(cpu, local_pci_probe, &ddi);
	else
		error = local_pci_probe(&ddi);

We end up in a situation where a worker thread gets the PF_USED_ASYNC
flag set instead of the modprobe thread.  As a result,
async_synchronize_full() is not invoked and modprobe completes without
waiting for the async code to finish.

The issue was discovered while loading the pm80xx driver:
(scsi_mod.scan=async)

modprobe pm80xx                      worker
...
  do_init_module()
  ...
    pci_call_probe()
      work_on_cpu(local_pci_probe)
                                     local_pci_probe()
                                       pm8001_pci_probe()
                                         scsi_scan_host()
                                           async_schedule()
                                           worker->flags |= PF_USED_ASYNC;
                                     ...
      < return from worker >
  ...
  if (current->flags & PF_USED_ASYNC) <--- false
  	async_synchronize_full();

Commit 21c3c5d2 ("block: don't request module during elevator init")
fixed the deadlock issue which the reverted commit 774a1221
("module, async: async_synchronize_full() on module init iff async is
used") tried to fix.

Since commit 0fdff3ec ("async, kmod: warn on synchronous
request_module() from async workers") synchronous module loading from
async is not allowed.

Given that the original deadlock issue is fixed and it is no longer
allowed to call synchronous request_module() from async we can remove
PF_USED_ASYNC flag to make module init consistently invoke
async_synchronize_full() unless async module probe is requested.
Signed-off-by: default avatarIgor Pylypiv <ipylypiv@google.com>
Reviewed-by: default avatarChangyuan Lyu <changyuanl@google.com>
Reviewed-by: default avatarLuis Chamberlain <mcgrof@kernel.org>
Acked-by: default avatarTejun Heo <tj@kernel.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      67d6212a
    • Linus Torvalds's avatar
      Merge branch 'for-5.17-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup · 305e6c42
      Linus Torvalds authored 
      Pull cgroup fixes from Tejun Heo:

 - Eric's fix for a long standing cgroup1 permission issue where it only
   checks for uid 0 instead of CAP which inadvertently allows
   unprivileged userns roots to modify release_agent userhelper

 - Fixes for the fallout from Waiman's recent cpuset work

* 'for-5.17-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
  cgroup/cpuset: Fix "suspicious RCU usage" lockdep warning
  cgroup-v1: Require capabilities to set release_agent
  cpuset: Fix the bug that subpart_cpus updated wrongly in update_cpumask()
  cgroup/cpuset: Make child cpusets restrict parents on v1 hierarchy
      305e6c42
    • Waiman Long's avatar
      cgroup/cpuset: Fix "suspicious RCU usage" lockdep warning · 2bdfd282
      Waiman Long authored 
      It was found that a "suspicious RCU usage" lockdep warning was issued
with the rcu_read_lock() call in update_sibling_cpumasks().  It is
because the update_cpumasks_hier() function may sleep. So we have
to release the RCU lock, call update_cpumasks_hier() and reacquire
it afterward.

Also add a percpu_rwsem_assert_held() in update_sibling_cpumasks()
instead of stating that in the comment.

Fixes: 4716909c ("cpuset: Track cpusets that use parent's effective_cpus")
Signed-off-by: default avatarWaiman Long <longman@redhat.com>
Tested-by: default avatarPhil Auld <pauld@redhat.com>
Reviewed-by: default avatarPhil Auld <pauld@redhat.com>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      2bdfd282
    • John Hubbard's avatar
      Revert "mm/gup: small refactoring: simplify try_grab_page()" · c36c04c2
      John Hubbard authored 
      This reverts commit 54d516b1

That commit did a refactoring that effectively combined fast and slow
gup paths (again).  And that was again incorrect, for two reasons:

 a) Fast gup and slow gup get reference counts on pages in different
    ways and with different goals: see Linus' writeup in commit
    cd1adf1b ("Revert "mm/gup: remove try_get_page(), call
    try_get_compound_head() directly""), and

 b) try_grab_compound_head() also has a specific check for
    "FOLL_LONGTERM && !is_pinned(page)", that assumes that the caller
    can fall back to slow gup. This resulted in new failures, as
    recently report by Will McVicker [1].

But (a) has problems too, even though they may not have been reported
yet.  So just revert this.

Link: https://lore.kernel.org/r/20220131203504.3458775-1-willmcvicker@google.com [1]
Fixes: 54d516b1 ("mm/gup: small refactoring: simplify try_grab_page()")
Reported-and-tested-by: default avatarWill McVicker <willmcvicker@google.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Minchan Kim <minchan@google.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: stable@vger.kernel.org # 5.15
Signed-off-by: default avatarJohn Hubbard <jhubbard@nvidia.com>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      c36c04c2
    • Linus Torvalds's avatar
      Merge tag 'mips-fixes-5.17_2' of git://git.kernel.org/pub/scm/linux/kernel/git/mips/linux · d394bb77
      Linus Torvalds authored 
      Pull MIPS fixes from Thomas Bogendoerfer:

 - fix missed change for PTR->PTR_WD conversion

 - kernel-doc fixes

* tag 'mips-fixes-5.17_2' of git://git.kernel.org/pub/scm/linux/kernel/git/mips/linux:
  MIPS: KVM: fix vz.c kernel-doc notation
  MIPS: octeon: Fix missed PTR->PTR_WD conversion
      d394bb77
  3. 02 Feb, 2022 4 commits
  5. 01 Feb, 2022 12 commits
  7. 31 Jan, 2022 2 commits
  9. 30 Jan, 2022 17 commits
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