perfctr seqlocks 3/4: ppc64 changes
- use write_perfseq_begin/end in perfctr_cpu_suspend/resume/sample
to indicate that the state has changed
- in mmap:ed state, redefine samplecnt field as the sequence number
Signed-off-by: Mikael Pettersson <[email protected]>
drivers/perfctr/ppc64.c | 10 ++++++++--
include/asm-ppc64/perfctr.h | 10 ++++------
2 files changed, 12 insertions(+), 8 deletions(-)
diff -rupN linux-2.6.12-rc5-mm1/drivers/perfctr/ppc64.c linux-2.6.12-rc5-mm1.perfctr-seqlock-ppc64/drivers/perfctr/ppc64.c
--- linux-2.6.12-rc5-mm1/drivers/perfctr/ppc64.c 2005-05-26 00:24:22.000000000 +0200
+++ linux-2.6.12-rc5-mm1.perfctr-seqlock-ppc64/drivers/perfctr/ppc64.c 2005-05-26 03:01:37.000000000 +0200
@@ -537,6 +537,8 @@ void perfctr_cpu_suspend(struct perfctr_
unsigned int i, cstatus;
struct perfctr_low_ctrs now;
+ write_perfseq_begin(&state->user.sequence);
+
/* quiesce the counters */
mtspr(SPRN_MMCR0, MMCR0_FC);
get_cpu_cache()->ppc64_mmcr0 = MMCR0_FC;
@@ -551,6 +553,8 @@ void perfctr_cpu_suspend(struct perfctr_
for (i = 0; i < perfctr_cstatus_nractrs(cstatus); ++i)
state->user.pmc[i].sum += (u32)(now.pmc[i]-state->user.pmc[i].start);
+
+ write_perfseq_end(&state->user.sequence);
}
void perfctr_cpu_resume(struct perfctr_cpu_state *state)
@@ -558,6 +562,7 @@ void perfctr_cpu_resume(struct perfctr_c
struct perfctr_low_ctrs now;
unsigned int i, cstatus;
+ write_perfseq_begin(&state->user.sequence);
if (perfctr_cstatus_has_ictrs(state->user.cstatus))
perfctr_cpu_iresume(state);
perfctr_cpu_write_control(state);
@@ -570,7 +575,7 @@ void perfctr_cpu_resume(struct perfctr_c
for (i = 0; i < perfctr_cstatus_nractrs(cstatus); ++i)
state->user.pmc[i].start = now.pmc[i];
- ++state->user.samplecnt;
+ write_perfseq_end(&state->user.sequence);
}
void perfctr_cpu_sample(struct perfctr_cpu_state *state)
@@ -578,6 +583,7 @@ 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)) {
@@ -589,7 +595,7 @@ void perfctr_cpu_sample(struct perfctr_c
state->user.pmc[i].sum += (u32)(now.pmc[i]-state->user.pmc[i].start);
state->user.pmc[i].start = now.pmc[i];
}
- ++state->user.samplecnt;
+ write_perfseq_end(&state->user.sequence);
}
static void perfctr_cpu_clear_counters(void)
diff -rupN linux-2.6.12-rc5-mm1/include/asm-ppc64/perfctr.h linux-2.6.12-rc5-mm1.perfctr-seqlock-ppc64/include/asm-ppc64/perfctr.h
--- linux-2.6.12-rc5-mm1/include/asm-ppc64/perfctr.h 2005-05-26 00:24:23.000000000 +0200
+++ linux-2.6.12-rc5-mm1.perfctr-seqlock-ppc64/include/asm-ppc64/perfctr.h 2005-05-26 03:01:37.000000000 +0200
@@ -22,12 +22,10 @@ struct perfctr_cpu_control_header {
struct perfctr_cpu_state_user {
__u32 cstatus;
- /* 'samplecnt' is incremented every time the 'start'
- fields have been updated by a sampling operation.
- Unfortunately the PPC timebase (tsc_start) has too
- low frequency for it to be a reliable context-switch
- indicator for user-space. */
- __u32 samplecnt;
+ /* 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 {
-
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