From: Mikael Pettersson <mikpe@csd.uu.se>
perfctr seqlocks 4/4: ppc32 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 <mikpe@csd.uu.se>
Signed-off-by: Andrew Morton <akpm@osdl.org>
---
drivers/perfctr/ppc.c | 8 ++++++--
include/asm-ppc/perfctr.h | 10 ++++------
2 files changed, 10 insertions(+), 8 deletions(-)
diff -puN drivers/perfctr/ppc.c~perfctr-seqlocks-for-mmaped-state-ppc32 drivers/perfctr/ppc.c
--- 25/drivers/perfctr/ppc.c~perfctr-seqlocks-for-mmaped-state-ppc32 2005-05-26 22:57:44.000000000 -0700
+++ 25-akpm/drivers/perfctr/ppc.c 2005-05-26 22:57:44.000000000 -0700
@@ -697,6 +697,7 @@ 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_mmcr0_quirk(state->user.cstatus)) {
unsigned int mmcr0 = mfspr(SPRN_MMCR0);
mtspr(SPRN_MMCR0, mmcr0 | MMCR0_FC);
@@ -712,10 +713,12 @@ void perfctr_cpu_suspend(struct perfctr_
nractrs = perfctr_cstatus_nractrs(cstatus);
for(i = 0; i < nractrs; ++i)
state->user.pmc[i].sum += now.pmc[i] - state->user.pmc[i].start;
+ 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);
if (perfctr_cstatus_has_mmcr0_quirk(state->user.cstatus))
@@ -733,7 +736,7 @@ void perfctr_cpu_resume(struct perfctr_c
for(i = 0; i < nrctrs; ++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)
@@ -741,6 +744,7 @@ 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)) {
@@ -752,7 +756,7 @@ 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];
}
- ++state->user.samplecnt;
+ write_perfseq_end(&state->user.sequence);
}
static void perfctr_cpu_clear_counters(void)
diff -puN include/asm-ppc/perfctr.h~perfctr-seqlocks-for-mmaped-state-ppc32 include/asm-ppc/perfctr.h
--- 25/include/asm-ppc/perfctr.h~perfctr-seqlocks-for-mmaped-state-ppc32 2005-05-26 22:57:44.000000000 -0700
+++ 25-akpm/include/asm-ppc/perfctr.h 2005-05-26 22:57:44.000000000 -0700
@@ -21,12 +21,10 @@ 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 {
_