perfctr seqlocks 2/4: x86 changes
- use write_perfseq_begin/end in perfctr_cpu_suspend/resume/sample
to indicate that the state has changed
- in mmap:ed state, redefine filler field as the sequence number
Signed-off-by: Mikael Pettersson <[email protected]>
drivers/perfctr/x86.c | 7 ++++++-
include/asm-i386/perfctr.h | 5 ++++-
2 files changed, 10 insertions(+), 2 deletions(-)
diff -rupN linux-2.6.12-rc5-mm1/drivers/perfctr/x86.c linux-2.6.12-rc5-mm1.perfctr-seqlock-x86/drivers/perfctr/x86.c
--- linux-2.6.12-rc5-mm1/drivers/perfctr/x86.c 2005-05-26 00:24:22.000000000 +0200
+++ linux-2.6.12-rc5-mm1.perfctr-seqlock-x86/drivers/perfctr/x86.c 2005-05-26 02:57:55.000000000 +0200
@@ -1162,6 +1162,7 @@ void perfctr_cpu_suspend(struct perfctr_
unsigned int i, cstatus, nractrs;
struct perfctr_low_ctrs now;
+ write_perfseq_begin(&state->user.sequence);
if (perfctr_cstatus_has_ictrs(state->user.cstatus))
perfctr_cpu_isuspend(state);
perfctr_cpu_read_counters(state, &now);
@@ -1172,10 +1173,12 @@ void perfctr_cpu_suspend(struct perfctr_
for(i = 0; i < nractrs; ++i)
state->user.pmc[i].sum += now.pmc[i] - state->user.pmc[i].start;
/* perfctr_cpu_disable_rdpmc(); */ /* not for x86 */
+ write_perfseq_end(&state->user.sequence);
}
void perfctr_cpu_resume(struct perfctr_cpu_state *state)
{
+ write_perfseq_begin(&state->user.sequence);
if (perfctr_cstatus_has_ictrs(state->user.cstatus))
perfctr_cpu_iresume(state);
/* perfctr_cpu_enable_rdpmc(); */ /* not for x86 or global-mode */
@@ -1192,7 +1195,7 @@ void perfctr_cpu_resume(struct perfctr_c
for(i = 0; i < nrctrs; ++i)
state->user.pmc[i].start = now.pmc[i];
}
- /* XXX: if (SMP && start.tsc == now.tsc) ++now.tsc; */
+ write_perfseq_end(&state->user.sequence);
}
void perfctr_cpu_sample(struct perfctr_cpu_state *state)
@@ -1200,6 +1203,7 @@ void perfctr_cpu_sample(struct perfctr_c
unsigned int i, cstatus, nractrs;
struct perfctr_low_ctrs now;
+ write_perfseq_begin(&state->user.sequence);
perfctr_cpu_read_counters(state, &now);
cstatus = state->user.cstatus;
if (perfctr_cstatus_has_tsc(cstatus)) {
@@ -1211,6 +1215,7 @@ void perfctr_cpu_sample(struct perfctr_c
state->user.pmc[i].sum += now.pmc[i] - state->user.pmc[i].start;
state->user.pmc[i].start = now.pmc[i];
}
+ write_perfseq_end(&state->user.sequence);
}
static void (*clear_counters)(void);
diff -rupN linux-2.6.12-rc5-mm1/include/asm-i386/perfctr.h linux-2.6.12-rc5-mm1.perfctr-seqlock-x86/include/asm-i386/perfctr.h
--- linux-2.6.12-rc5-mm1/include/asm-i386/perfctr.h 2005-05-26 00:24:23.000000000 +0200
+++ linux-2.6.12-rc5-mm1.perfctr-seqlock-x86/include/asm-i386/perfctr.h 2005-05-26 02:57:55.000000000 +0200
@@ -21,7 +21,10 @@ struct perfctr_cpu_control_header {
struct perfctr_cpu_state_user {
__u32 cstatus;
- __u32 _filler;
+ /* This is a sequence counter to ensure atomic reads by
+ * userspace. The mechanism is identical to that used for
+ * seqcount_t in include/linux/seqlock.h. */
+ __u32 sequence;
__u64 tsc_start;
__u64 tsc_sum;
struct {