Jens, just a FYI about this stuff, not yet ready for reviewing.
Hi Frédéric, Steven,
Have you guys ever get into this kind of situation?
[root@mica linux-2.6-tip]# cat /sys/kernel/debug/tracing/trace | tail
kjournald-480 [000] 593.219805: C W 2149459 + 8 [0]
<idle>-0 [000] 593.219849: A WS 2149467 + 8 <- (8,2) 44952
kjournald-480 [000] 607.210959: Q WS 2149467 + 8
kjournald-480 [000] 607.210960: G WS 2149467 + 8
kjournald-480 [000] 607.210963: P N
kjournald-480 [000] 607.210964: I W 2149467 + 8
kjournald-480 [000] 607.210965: D W 2149467 + 8
kjournald-480 [000] 607.210967: U N 1
kjournald-480 [000] 607.210971: C W 2149467 + 8 [0]
<idle>-0 [000] 607.211049: [root@mica linux-2.6-tip]#
[root@mica linux-2.6-tip]# head /sys/kernel/debug/tracing/trace
# tracer: blk
#
# TASK-PID CPU# TIMESTAMP FUNCTION
# | | | | |
A W 2147707 + 8 <- (8,2) 43192
kjournald-480 [000] 254.428659: Q W 2147707 + 8
kjournald-480 [000] 254.428661: G W 2147707 + 8
kjournald-480 [000] 254.428663: I W 100410211 + 8
pdflush-261 [000] 147.328259: P N
kjournald-480 [000] 254.428664: I W 2147707 + 8
[root@mica linux-2.6-tip]#
This is happening in an experiment I'm doing in porting blktrace to the
tracing/ring_buffer infrastructure, the problem always happens at this
function:
static int blk_log_remap(struct trace_seq *s, struct blk_io_entry *t)
{
char rwbs[6];
struct blk_io_trace_remap r = { .device = 0, };
get_pdu_remap(t, &r);
t->device = r.device_from;
fill_rwbs(rwbs, t);
return trace_seq_printf(s, " A %3s %llu + %u <- (%d,%d) %llu\n",
rwbs, (unsigned long long)t->sector,
t_sec(t), MAJOR(r.device), MINOR(r.device),
(unsigned long long)r.sector);
}
And the registered .print_line routine does check the return of
trace_seq_printf:
if (!ret)
return TRACE_TYPE_PARTIAL_LINE;
}
default:
return TRACE_TYPE_UNHANDLED;
}
return TRACE_TYPE_HANDLED;
}
Full patch, still WIPish:
http://oops.ghostprotocols.net:81/acme/blkftrace.patch
- Arnaldo
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