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Subject[GIT pull] perf fixes for 4.15
Linus,

please pull the latest perf-urgent-for-linus git tree from:

git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git perf-urgent-for-linus

Four patches which all address lock inversions and deadlocks in the perf
core code and the Intel debug store.

Thanks,

tglx

------------------>
Peter Zijlstra (4):
perf/core: Fix lock inversion between perf,trace,cpuhp
perf/core: Fix another perf,trace,cpuhp lock inversion
perf/core: Fix ctx::mutex deadlock
perf/x86: Fix perf,x86,cpuhp deadlock


arch/x86/events/intel/ds.c | 33 +++++++++++++++++---------------
kernel/events/core.c | 47 +++++++++++++++++++++++++++++++++++++++++-----
2 files changed, 60 insertions(+), 20 deletions(-)

diff --git a/arch/x86/events/intel/ds.c b/arch/x86/events/intel/ds.c
index 8156e47da7ba..18c25ab28557 100644
--- a/arch/x86/events/intel/ds.c
+++ b/arch/x86/events/intel/ds.c
@@ -372,10 +372,9 @@ static int alloc_pebs_buffer(int cpu)
static void release_pebs_buffer(int cpu)
{
struct cpu_hw_events *hwev = per_cpu_ptr(&cpu_hw_events, cpu);
- struct debug_store *ds = hwev->ds;
void *cea;

- if (!ds || !x86_pmu.pebs)
+ if (!x86_pmu.pebs)
return;

kfree(per_cpu(insn_buffer, cpu));
@@ -384,7 +383,6 @@ static void release_pebs_buffer(int cpu)
/* Clear the fixmap */
cea = &get_cpu_entry_area(cpu)->cpu_debug_buffers.pebs_buffer;
ds_clear_cea(cea, x86_pmu.pebs_buffer_size);
- ds->pebs_buffer_base = 0;
dsfree_pages(hwev->ds_pebs_vaddr, x86_pmu.pebs_buffer_size);
hwev->ds_pebs_vaddr = NULL;
}
@@ -419,16 +417,14 @@ static int alloc_bts_buffer(int cpu)
static void release_bts_buffer(int cpu)
{
struct cpu_hw_events *hwev = per_cpu_ptr(&cpu_hw_events, cpu);
- struct debug_store *ds = hwev->ds;
void *cea;

- if (!ds || !x86_pmu.bts)
+ if (!x86_pmu.bts)
return;

/* Clear the fixmap */
cea = &get_cpu_entry_area(cpu)->cpu_debug_buffers.bts_buffer;
ds_clear_cea(cea, BTS_BUFFER_SIZE);
- ds->bts_buffer_base = 0;
dsfree_pages(hwev->ds_bts_vaddr, BTS_BUFFER_SIZE);
hwev->ds_bts_vaddr = NULL;
}
@@ -454,16 +450,22 @@ void release_ds_buffers(void)
if (!x86_pmu.bts && !x86_pmu.pebs)
return;

- get_online_cpus();
- for_each_online_cpu(cpu)
+ for_each_possible_cpu(cpu)
+ release_ds_buffer(cpu);
+
+ for_each_possible_cpu(cpu) {
+ /*
+ * Again, ignore errors from offline CPUs, they will no longer
+ * observe cpu_hw_events.ds and not program the DS_AREA when
+ * they come up.
+ */
fini_debug_store_on_cpu(cpu);
+ }

for_each_possible_cpu(cpu) {
release_pebs_buffer(cpu);
release_bts_buffer(cpu);
- release_ds_buffer(cpu);
}
- put_online_cpus();
}

void reserve_ds_buffers(void)
@@ -483,8 +485,6 @@ void reserve_ds_buffers(void)
if (!x86_pmu.pebs)
pebs_err = 1;

- get_online_cpus();
-
for_each_possible_cpu(cpu) {
if (alloc_ds_buffer(cpu)) {
bts_err = 1;
@@ -521,11 +521,14 @@ void reserve_ds_buffers(void)
if (x86_pmu.pebs && !pebs_err)
x86_pmu.pebs_active = 1;

- for_each_online_cpu(cpu)
+ for_each_possible_cpu(cpu) {
+ /*
+ * Ignores wrmsr_on_cpu() errors for offline CPUs they
+ * will get this call through intel_pmu_cpu_starting().
+ */
init_debug_store_on_cpu(cpu);
+ }
}
-
- put_online_cpus();
}

/*
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 4df5b695bf0d..5d8f4031f8d5 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -1231,6 +1231,10 @@ static void put_ctx(struct perf_event_context *ctx)
* perf_event_context::lock
* perf_event::mmap_mutex
* mmap_sem
+ *
+ * cpu_hotplug_lock
+ * pmus_lock
+ * cpuctx->mutex / perf_event_context::mutex
*/
static struct perf_event_context *
perf_event_ctx_lock_nested(struct perf_event *event, int nesting)
@@ -4196,6 +4200,7 @@ int perf_event_release_kernel(struct perf_event *event)
{
struct perf_event_context *ctx = event->ctx;
struct perf_event *child, *tmp;
+ LIST_HEAD(free_list);

/*
* If we got here through err_file: fput(event_file); we will not have
@@ -4268,8 +4273,7 @@ int perf_event_release_kernel(struct perf_event *event)
struct perf_event, child_list);
if (tmp == child) {
perf_remove_from_context(child, DETACH_GROUP);
- list_del(&child->child_list);
- free_event(child);
+ list_move(&child->child_list, &free_list);
/*
* This matches the refcount bump in inherit_event();
* this can't be the last reference.
@@ -4284,6 +4288,11 @@ int perf_event_release_kernel(struct perf_event *event)
}
mutex_unlock(&event->child_mutex);

+ list_for_each_entry_safe(child, tmp, &free_list, child_list) {
+ list_del(&child->child_list);
+ free_event(child);
+ }
+
no_ctx:
put_event(event); /* Must be the 'last' reference */
return 0;
@@ -8516,6 +8525,29 @@ perf_event_set_addr_filter(struct perf_event *event, char *filter_str)
return ret;
}

+static int
+perf_tracepoint_set_filter(struct perf_event *event, char *filter_str)
+{
+ struct perf_event_context *ctx = event->ctx;
+ int ret;
+
+ /*
+ * Beware, here be dragons!!
+ *
+ * the tracepoint muck will deadlock against ctx->mutex, but the tracepoint
+ * stuff does not actually need it. So temporarily drop ctx->mutex. As per
+ * perf_event_ctx_lock() we already have a reference on ctx.
+ *
+ * This can result in event getting moved to a different ctx, but that
+ * does not affect the tracepoint state.
+ */
+ mutex_unlock(&ctx->mutex);
+ ret = ftrace_profile_set_filter(event, event->attr.config, filter_str);
+ mutex_lock(&ctx->mutex);
+
+ return ret;
+}
+
static int perf_event_set_filter(struct perf_event *event, void __user *arg)
{
char *filter_str;
@@ -8532,8 +8564,7 @@ static int perf_event_set_filter(struct perf_event *event, void __user *arg)

if (IS_ENABLED(CONFIG_EVENT_TRACING) &&
event->attr.type == PERF_TYPE_TRACEPOINT)
- ret = ftrace_profile_set_filter(event, event->attr.config,
- filter_str);
+ ret = perf_tracepoint_set_filter(event, filter_str);
else if (has_addr_filter(event))
ret = perf_event_set_addr_filter(event, filter_str);

@@ -9168,7 +9199,13 @@ static int perf_try_init_event(struct pmu *pmu, struct perf_event *event)
if (!try_module_get(pmu->module))
return -ENODEV;

- if (event->group_leader != event) {
+ /*
+ * A number of pmu->event_init() methods iterate the sibling_list to,
+ * for example, validate if the group fits on the PMU. Therefore,
+ * if this is a sibling event, acquire the ctx->mutex to protect
+ * the sibling_list.
+ */
+ if (event->group_leader != event && pmu->task_ctx_nr != perf_sw_context) {
/*
* This ctx->mutex can nest when we're called through
* inheritance. See the perf_event_ctx_lock_nested() comment.
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