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| author |   Al Viro <viro@zeniv.linux.org.uk> | 2017-04-02 10:33:48 -0400 |
|---|---|---|
| committer | Al Viro <viro@zeniv.linux.org.uk> | 2017-04-02 10:33:48 -0400 |
| commit | bee3f412d6fc94011850f16cddce745d529411a5 (patch) | |
| tree | 01b1823a3bc0cb760129ed15f7ec027a36edc48b /arch/x86/events/core.c | |
| parent | generic ...copy_..._user primitives (diff) | |
| parent | parisc: Avoid stalled CPU warnings after system shutdown (diff) | |
| download | linux-dev-bee3f412d6fc94011850f16cddce745d529411a5.tar.xz linux-dev-bee3f412d6fc94011850f16cddce745d529411a5.zip | |
Merge branch 'parisc-4.11-3' of git://git.kernel.org/pub/scm/linux/kernel/git/deller/parisc-linux into uaccess.parisc
Diffstat (limited to 'arch/x86/events/core.c')
| -rw-r--r-- | arch/x86/events/core.c | 16 |
1 files changed, 14 insertions, 2 deletions
diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c index 349d4d17aa7f..2aa1ad194db2 100644 --- a/arch/x86/events/core.c +++ b/arch/x86/events/core.c @@ -2101,8 +2101,8 @@ static int x86_pmu_event_init(struct perf_event *event) static void refresh_pce(void *ignored) { - if (current->mm) - load_mm_cr4(current->mm); + if (current->active_mm) + load_mm_cr4(current->active_mm); } static void x86_pmu_event_mapped(struct perf_event *event) @@ -2110,6 +2110,18 @@ static void x86_pmu_event_mapped(struct perf_event *event) if (!(event->hw.flags & PERF_X86_EVENT_RDPMC_ALLOWED)) return; + /* + * This function relies on not being called concurrently in two + * tasks in the same mm. Otherwise one task could observe + * perf_rdpmc_allowed > 1 and return all the way back to + * userspace with CR4.PCE clear while another task is still + * doing on_each_cpu_mask() to propagate CR4.PCE. + * + * For now, this can't happen because all callers hold mmap_sem + * for write. If this changes, we'll need a different solution. + */ + lockdep_assert_held_exclusive(¤t->mm->mmap_sem); + if (atomic_inc_return(¤t->mm->context.perf_rdpmc_allowed) == 1) on_each_cpu_mask(mm_cpumask(current->mm), refresh_pce, NULL, 1); } |