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Date: Tue, 16 Dec 2008 12:10:03 -0200 From: Arnaldo Carvalho de Melo <acme@...hat.com> To: Frédéric Weisbecker <fweisbec@...il.com> Cc: Steven Rostedt <rostedt@...dmis.org>, Ingo Molnar <mingo@...e.hu>, Jens Axboe <jens.axboe@...cle.com>, Linux Kernel <linux-kernel@...r.kernel.org> Subject: trace_seq_printf/.print_line question 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@...a 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@...a linux-2.6-tip]# [root@...a 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@...a 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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