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SubjectRe: [patch 1/2] oProfile: oops when profile_pc() return ~0LU
On Tue, 23 Oct 2007 at 13:10 +0000, Sami Farin wrote:
> On Mon, Oct 22, 2007 at 19:38:10 -0700, Linus Torvalds wrote:
> >
> > This set of two patches look ok by me, but I'd like sign-offs.. Also, were
> > they tested and found to fix the problem by Sami?
> >
> > Linus

For the signed-offs I thought the From: was an implicit Signed-offs.

Test was done privately, Sami helped to narrow down the trouble, but
he didn't test the last patch, nothing bad on Sami side, I was too
confident the fix was obvious after narrowing it.

>
> The previous patch I tested by Philippe, oprof-fix-profile_pc-use.patch,
> worked ok, but with this latest patch oprofiled aborts.
> But kernel does not oops or print msgs.

argh, I just moved the wrong eip from kernel to user space where the same
problem occur too, *sighs*, since I can't reproduce Sami problem, my own
test obviously worked...

Sami, can you test this new patch. After testing can you report
the contents of /dev/oprofile/stats/cpu*/sample_invalid_eip ?

Linus, there is two way to fix this problem, the attached patch fix it
by sanitizing the sampled eip, the other is to replace the use of
profile_pc(); by instruction_pointer(); in cpu_buffer.c, that one was
tested by Sami but 1) it'll break the 'use oprofile as a sort of lockometer'
2) I think sanitizing the eip will be necessary anyway as I'm not really
confident than instruction_pointer() can never return weird eip on some
weird arch and/or some weird circumstances.

diff --git a/drivers/oprofile/cpu_buffer.c b/drivers/oprofile/cpu_buffer.c
index a83c3db..c93d3d2 100644
--- a/drivers/oprofile/cpu_buffer.c
+++ b/drivers/oprofile/cpu_buffer.c
@@ -64,6 +64,8 @@ int alloc_cpu_buffers(void)
b->head_pos = 0;
b->sample_received = 0;
b->sample_lost_overflow = 0;
+ b->backtrace_aborted = 0;
+ b->sample_invalid_eip = 0;
b->cpu = i;
INIT_DELAYED_WORK(&b->work, wq_sync_buffer);
}
@@ -175,6 +177,11 @@ static int log_sample(struct oprofile_cpu_buffer * cpu_buf, unsigned long pc,

cpu_buf->sample_received++;

+ if (pc == ESCAPE_CODE) {
+ cpu_buf->sample_invalid_eip++;
+ return 0;
+ }
+
if (nr_available_slots(cpu_buf) < 3) {
cpu_buf->sample_lost_overflow++;
return 0;
diff --git a/drivers/oprofile/cpu_buffer.h b/drivers/oprofile/cpu_buffer.h
index 49900d9..c66c025 100644
--- a/drivers/oprofile/cpu_buffer.h
+++ b/drivers/oprofile/cpu_buffer.h
@@ -42,6 +42,7 @@ struct oprofile_cpu_buffer {
unsigned long sample_received;
unsigned long sample_lost_overflow;
unsigned long backtrace_aborted;
+ unsigned long sample_invalid_eip;
int cpu;
struct delayed_work work;
} ____cacheline_aligned;
diff --git a/drivers/oprofile/oprofile_stats.c b/drivers/oprofile/oprofile_stats.c
index f0acb66..d1f6d77 100644
--- a/drivers/oprofile/oprofile_stats.c
+++ b/drivers/oprofile/oprofile_stats.c
@@ -26,6 +26,8 @@ void oprofile_reset_stats(void)
cpu_buf = &cpu_buffer[i];
cpu_buf->sample_received = 0;
cpu_buf->sample_lost_overflow = 0;
+ cpu_buf->backtrace_aborted = 0;
+ cpu_buf->sample_invalid_eip = 0;
}

atomic_set(&oprofile_stats.sample_lost_no_mm, 0);
@@ -61,6 +63,8 @@ void oprofile_create_stats_files(struct super_block * sb, struct dentry * root)
&cpu_buf->sample_lost_overflow);
oprofilefs_create_ro_ulong(sb, cpudir, "backtrace_aborted",
&cpu_buf->backtrace_aborted);
+ oprofilefs_create_ro_ulong(sb, cpudir, "sample_invalid_eip",
+ &cpu_buf->sample_invalid_eip);
}

oprofilefs_create_ro_atomic(sb, dir, "sample_lost_no_mm",
-
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