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perf/x86/intel/bts: Fix DS area sharing with x86_pmu events 

Currently, the intel_bts driver relies on the DS area allocated by the x86_pmu
code in its event_init() path, which is a bug: creating a BTS event while
no x86_pmu events are present results in a NULL pointer dereference.

The same DS area is also used by PEBS sampling, which makes it quite a bit
trickier to have a separate one for intel_bts' purposes.

This patch makes intel_bts driver use the same DS allocation and reference
counting code as x86_pmu to make sure it is always present when either
intel_bts or x86_pmu need it.

Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: acme@infradead.org
Cc: adrian.hunter@intel.com
Link: http://lkml.kernel.org/r/1434024837-9916-2-git-send-email-alexander.shishkin@linux.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Alexander Shishkin 2015-06-11 15:13:56 +03:00 committed by Ingo Molnar
parent 4b36f1a413
commit 6b099d9b04
3 changed files with 46 additions and 19 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

52
arch/x86/kernel/cpu/perf_event.c
View File

@ -270,11 +270,7 @@ static bool check_hw_exists(void)
static void hw_perf_event_destroy(struct perf_event *event)
{
if (atomic_dec_and_mutex_lock(&active_events, &pmc_reserve_mutex)) {
release_pmc_hardware();
release_ds_buffers();
mutex_unlock(&pmc_reserve_mutex);
}
x86_release_hardware();
}
void hw_perf_lbr_event_destroy(struct perf_event *event)
@ -324,6 +320,35 @@ set_ext_hw_attr(struct hw_perf_event *hwc, struct perf_event *event)
return x86_pmu_extra_regs(val, event);
}
int x86_reserve_hardware(void)
{
int err = 0;
if (!atomic_inc_not_zero(&active_events)) {
mutex_lock(&pmc_reserve_mutex);
if (atomic_read(&active_events) == 0) {
if (!reserve_pmc_hardware())
err = -EBUSY;
else
reserve_ds_buffers();
}
if (!err)
atomic_inc(&active_events);
mutex_unlock(&pmc_reserve_mutex);
}
return err;
}
void x86_release_hardware(void)
{
if (atomic_dec_and_mutex_lock(&active_events, &pmc_reserve_mutex)) {
release_pmc_hardware();
release_ds_buffers();
mutex_unlock(&pmc_reserve_mutex);
}
}
/*
* Check if we can create event of a certain type (that no conflicting events
* are present).
@ -336,9 +361,10 @@ int x86_add_exclusive(unsigned int what)
return 0;
mutex_lock(&pmc_reserve_mutex);
for (i = 0; i < ARRAY_SIZE(x86_pmu.lbr_exclusive); i++)
for (i = 0; i < ARRAY_SIZE(x86_pmu.lbr_exclusive); i++) {
if (i != what && atomic_read(&x86_pmu.lbr_exclusive[i]))
goto out;
}
atomic_inc(&x86_pmu.lbr_exclusive[what]);
ret = 0;
@ -527,19 +553,7 @@ static int __x86_pmu_event_init(struct perf_event *event)
if (!x86_pmu_initialized())
return -ENODEV;
err = 0;
if (!atomic_inc_not_zero(&active_events)) {
mutex_lock(&pmc_reserve_mutex);
if (atomic_read(&active_events) == 0) {
if (!reserve_pmc_hardware())
err = -EBUSY;
else
reserve_ds_buffers();
}
if (!err)
atomic_inc(&active_events);
mutex_unlock(&pmc_reserve_mutex);
}
err = x86_reserve_hardware();
if (err)
return err;

4
arch/x86/kernel/cpu/perf_event.h
View File

@ -703,6 +703,10 @@ int x86_add_exclusive(unsigned int what);
void x86_del_exclusive(unsigned int what);
int x86_reserve_hardware(void);
void x86_release_hardware(void);
void hw_perf_lbr_event_destroy(struct perf_event *event);
int x86_setup_perfctr(struct perf_event *event);

9
arch/x86/kernel/cpu/perf_event_intel_bts.c
View File

@ -483,17 +483,26 @@ static int bts_event_add(struct perf_event *event, int mode)
static void bts_event_destroy(struct perf_event *event)
{
x86_release_hardware();
x86_del_exclusive(x86_lbr_exclusive_bts);
}
static int bts_event_init(struct perf_event *event)
{
int ret;
if (event->attr.type != bts_pmu.type)
return -ENOENT;
if (x86_add_exclusive(x86_lbr_exclusive_bts))
return -EBUSY;
ret = x86_reserve_hardware();
if (ret) {
x86_del_exclusive(x86_lbr_exclusive_bts);
return ret;
}
event->destroy = bts_event_destroy;
return 0;