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authorPaul Mackerras <paulus@samba.org>2009-02-09 06:42:47 -0500
committerIngo Molnar <mingo@elte.hu>2009-02-09 06:47:16 -0500
commit23a185ca8abbeef64b6ffc33059b1d630e43ec10 (patch)
treec5eb9454ff969377adb40532119240f6fc893fcb /include/linux/sched.h
parent82aa9a1829199233f9bdaf26e2ee271114f4701e (diff)
perf_counters: make software counters work as per-cpu counters
Impact: kernel crash fix Yanmin Zhang reported that using a PERF_COUNT_TASK_CLOCK software counter as a per-cpu counter would reliably crash the system, because it calls __task_delta_exec with a null pointer. The page fault, context switch and cpu migration counters also won't function correctly as per-cpu counters since they reference the current task. This fixes the problem by redirecting the task_clock counter to the cpu_clock counter when used as a per-cpu counter, and by implementing per-cpu page fault, context switch and cpu migration counters. Along the way, this: - Initializes counter->ctx earlier, in perf_counter_alloc, so that sw_perf_counter_init can use it - Adds code to kernel/sched.c to count task migrations into each cpu, in rq->nr_migrations_in - Exports the per-cpu context switch and task migration counts via new functions added to kernel/sched.c - Makes sure that if sw_perf_counter_init fails, we don't try to initialize the counter as a hardware counter. Since the user has passed a negative, non-raw event type, they clearly don't intend for it to be interpreted as a hardware event. Reported-by: "Zhang Yanmin" <yanmin_zhang@linux.intel.com> Signed-off-by: Paul Mackerras <paulus@samba.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'include/linux/sched.h')
-rw-r--r--include/linux/sched.h2
1 files changed, 2 insertions, 0 deletions
diff --git a/include/linux/sched.h b/include/linux/sched.h
index b85b10abf770..1e5f70062a9c 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -137,6 +137,8 @@ extern unsigned long nr_running(void);
137extern unsigned long nr_uninterruptible(void); 137extern unsigned long nr_uninterruptible(void);
138extern unsigned long nr_active(void); 138extern unsigned long nr_active(void);
139extern unsigned long nr_iowait(void); 139extern unsigned long nr_iowait(void);
140extern u64 cpu_nr_switches(int cpu);
141extern u64 cpu_nr_migrations(int cpu);
140 142
141struct seq_file; 143struct seq_file;
142struct cfs_rq; 144struct cfs_rq;