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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: 94457b36e8 ("x86/intel_rdt: Add diagnostics when writing the cpus file")
Fixes: cfd0f34e4c ("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
This commit is contained in:
Xiaochen Shen 2019-11-07 06:36:36 +08:00 committed by Borislav Petkov
parent fc5db58539
commit c8eafe1495
1 changed files with 0 additions and 4 deletions
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4
arch/x86/kernel/cpu/resctrl/rdtgroup.c
View File

@ -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;
}