[tip: x86/urgent] x86/resctrl: Fix potential lockdep warning

tip-bot2 for Xiaochen Shen
2019-11-13T11:47:20Z

The following commit has been merged into the x86/urgent branch of tip:

Commit-ID: c8eafe1495303bfd0eedaa8156b1ee9082ee9642
Gitweb: https://git.kernel.org/tip/c8eafe1495303bfd0eedaa8156b1ee9082ee9642
Author: Xiaochen Shen <xiaochen.shen@intel.com>
AuthorDate: Thu, 07 Nov 2019 06:36:36 +08:00
Committer: Borislav Petkov <bp@suse.de>
CommitterDate: Wed, 13 Nov 2019 12:34:44 +01:00

x86/resctrl: Fix potential lockdep warning

rdtgroup_cpus_write() and mkdir_rdt_prepare() call
rdtgroup_kn_lock_live() -> kernfs_to_rdtgroup() to get 'rdtgrp', and
then call the rdt_last_cmd_{clear,puts,...}() functions which will check
if rdtgroup_mutex is held/requires its caller to hold rdtgroup_mutex.

But if 'rdtgrp' returned from kernfs_to_rdtgroup() is NULL,
rdtgroup_mutex is not held and calling rdt_last_cmd_{clear,puts,...}()
will result in a self-incurred, potential lockdep warning.

Remove the rdt_last_cmd_{clear,puts,...}() calls in these two paths.
Just returning error should be sufficient to report to the user that the
entry doesn't exist any more.

[ bp: Massage. ]

Fixes: 94457b36e8a5 ("x86/intel_rdt: Add diagnostics when writing the cpus file")
Fixes: cfd0f34e4cd5 ("x86/intel_rdt: Add diagnostics when making directories")
Signed-off-by: Xiaochen Shen <xiaochen.shen@intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Tony Luck <tony.luck@intel.com>
Reviewed-by: Fenghua Yu <fenghua.yu@intel.com>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: pei.p.jia@intel.com
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: x86-ml <x86@kernel.org>
Link: https://lkml.kernel.org/r/1573079796-11713-1-git-send-email-xiaochen.shen@intel.com
---
arch/x86/kernel/cpu/resctrl/rdtgroup.c | 4 ----
1 file changed, 4 deletions(-)

diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
index a46dee8..2e3b06d 100644
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
@@ -461,10 +461,8 @@ static ssize_t rdtgroup_cpus_write(struct kernfs_open_file *of,
}

rdtgrp = rdtgroup_kn_lock_live(of->kn);
- rdt_last_cmd_clear();
if (!rdtgrp) {
ret = -ENOENT;
- rdt_last_cmd_puts("Directory was removed\n");
goto unlock;
}

@@ -2648,10 +2646,8 @@ static int mkdir_rdt_prepare(struct kernfs_node *parent_kn,
int ret;

prdtgrp = rdtgroup_kn_lock_live(prgrp_kn);
- rdt_last_cmd_clear();
if (!prdtgrp) {
ret = -ENODEV;
- rdt_last_cmd_puts("Directory was removed\n");
goto out_unlock;
}