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| author | Thomas Gleixner <tglx@linutronix.de> | 2016-11-15 15:12:13 +0100 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2016-11-15 18:35:49 +0100 |
| commit | a2584e1d5a74e8f5387d6484ad4c73ded36aa2ae (patch) | |
| tree | f16c84942390d22b0b4c8a8142b4466d6c101211 /arch | |
| parent | x86/intel_rdt: Protect info directory from removal (diff) | |
| download | linux-a2584e1d5a74e8f5387d6484ad4c73ded36aa2ae.tar.xz linux-a2584e1d5a74e8f5387d6484ad4c73ded36aa2ae.zip | |
x86/intel_rdt: Prevent deadlock against hotplug lock
The cpu online/offline callbacks of intel_rdt lock rdtgroup_mutex nested
inside of cpu hotplug lock. rdtgroup_cpus_write() does it in reverse order.
Remove the get/put_online_cpus() calls from rdtgroup_cpus_write(). This is
safe against cpu hotplug as the resource group cpumasks are protected by
rdtgroup_mutex.
Found by review, but should have been found if authors would have bothered
to test cpu hotplug with lockdep enabled.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Shaohua Li <shli@fb.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Tony Luck <tony.luck@intel.com>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/x86/kernel/cpu/intel_rdt_rdtgroup.c | 8 |
1 files changed, 3 insertions, 5 deletions
diff --git a/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c b/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c index cff286e6d69f..2f54931e0fa9 100644 --- a/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c +++ b/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c @@ -207,6 +207,7 @@ static ssize_t rdtgroup_cpus_write(struct kernfs_open_file *of, free_cpumask_var(tmpmask); return -ENOMEM; } + rdtgrp = rdtgroup_kn_lock_live(of->kn); if (!rdtgrp) { ret = -ENOENT; @@ -217,12 +218,11 @@ static ssize_t rdtgroup_cpus_write(struct kernfs_open_file *of, if (ret) goto unlock; - get_online_cpus(); /* check that user didn't specify any offline cpus */ cpumask_andnot(tmpmask, newmask, cpu_online_mask); if (cpumask_weight(tmpmask)) { ret = -EINVAL; - goto end; + goto unlock; } /* Check whether cpus are dropped from this group */ @@ -231,7 +231,7 @@ static ssize_t rdtgroup_cpus_write(struct kernfs_open_file *of, /* Can't drop from default group */ if (rdtgrp == &rdtgroup_default) { ret = -EINVAL; - goto end; + goto unlock; } /* Give any dropped cpus to rdtgroup_default */ cpumask_or(&rdtgroup_default.cpu_mask, @@ -258,8 +258,6 @@ static ssize_t rdtgroup_cpus_write(struct kernfs_open_file *of, /* Done pushing/pulling - update this group with new mask */ cpumask_copy(&rdtgrp->cpu_mask, newmask); -end: - put_online_cpus(); unlock: rdtgroup_kn_unlock(of->kn); free_cpumask_var(tmpmask); |