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perf_counter: Fix race in counter initialization

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We need the PID namespace and counter ID available when the
counter overflows and we need to generate a sample event.

[ Impact: fix kernel crash with high-frequency sampling ]

Reported-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: John Kacur <jkacur@redhat.com>
LKML-Reference: <new-submission>
[ fixed a further crash and cleaned up the initialization a bit ]
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Peter Zijlstra 2009-06-03 14:01:36 +02:00 committed by Ingo Molnar
parent 8229289b60
commit a96bbc1641
1 changed files with 14 additions and 11 deletions
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25
kernel/perf_counter.c
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@ -48,6 +48,8 @@ int sysctl_perf_counter_priv __read_mostly; /* do we need to be privileged */
int sysctl_perf_counter_mlock __read_mostly = 512; /* 'free' kb per user */
int sysctl_perf_counter_limit __read_mostly = 100000; /* max NMIs per second */
static atomic64_t perf_counter_id;
/*
* Lock for (sysadmin-configurable) counter reservations:
*/
@ -3351,14 +3353,18 @@ perf_counter_alloc(struct perf_counter_attr *attr,
mutex_init(&counter->mmap_mutex);
counter->cpu = cpu;
counter->cpu = cpu;
counter->attr = *attr;
counter->group_leader = group_leader;
counter->pmu = NULL;
counter->ctx = ctx;
counter->oncpu = -1;
counter->group_leader = group_leader;
counter->pmu = NULL;
counter->ctx = ctx;
counter->oncpu = -1;
counter->ns = get_pid_ns(current->nsproxy->pid_ns);
counter->id = atomic64_inc_return(&perf_counter_id);
counter->state = PERF_COUNTER_STATE_INACTIVE;
counter->state = PERF_COUNTER_STATE_INACTIVE;
if (attr->disabled)
counter->state = PERF_COUNTER_STATE_OFF;
@ -3402,6 +3408,8 @@ done:
err = PTR_ERR(pmu);
if (err) {
if (counter->ns)
put_pid_ns(counter->ns);
kfree(counter);
return ERR_PTR(err);
}
@ -3419,8 +3427,6 @@ done:
return counter;
}
static atomic64_t perf_counter_id;
/**
* sys_perf_counter_open - open a performance counter, associate it to a task/cpu
*
@ -3515,9 +3521,6 @@ SYSCALL_DEFINE5(perf_counter_open,
list_add_tail(&counter->owner_entry, &current->perf_counter_list);
mutex_unlock(&current->perf_counter_mutex);
counter->ns = get_pid_ns(current->nsproxy->pid_ns);
counter->id = atomic64_inc_return(&perf_counter_id);
fput_light(counter_file, fput_needed2);
out_fput: