Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754348AbZFRIjZ (ORCPT ); Thu, 18 Jun 2009 04:39:25 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753291AbZFRIjR (ORCPT ); Thu, 18 Jun 2009 04:39:17 -0400 Received: from e23smtp06.au.ibm.com ([202.81.31.148]:41207 "EHLO e23smtp06.au.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752903AbZFRIjQ (ORCPT ); Thu, 18 Jun 2009 04:39:16 -0400 Date: Thu, 18 Jun 2009 14:08:52 +0530 From: "K.Prasad" To: Frederic Weisbecker Cc: Ingo Molnar , Linux Kernel Mailing List Subject: Re: [Patch 1/2] ksym_tracer:Fix line-wrapping after removal of ksym tracer entry Message-ID: <20090618083852.GA5793@in.ibm.com> Reply-To: prasad@linux.vnet.ibm.com References: <20090616225257.041883212@prasadkr_t60p.in.ibm.com> <20090616230504.GB14753@in.ibm.com> <20090617050605.GC7411@nowhere> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090617050605.GC7411@nowhere> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4127 Lines: 123 On Wed, Jun 17, 2009 at 07:06:07AM +0200, Frederic Weisbecker wrote: > On Wed, Jun 17, 2009 at 04:35:04AM +0530, K.Prasad wrote: > > Removal of a ksym entry results in missing information and an early return with > > TRACE_TYPE_PARTIAL_LINE code (minus the line return). This patch modifies the > > output function to unconditionally add a line return irrespective of the > > return code. > > > > Signed-off-by: K.Prasad > > --- > > kernel/trace/trace_ksym.c | 27 +++++++++++++++------------ > > 1 file changed, 15 insertions(+), 12 deletions(-) > > > > Index: linux-2.6-tip.hbkpt/kernel/trace/trace_ksym.c > > =================================================================== > > --- linux-2.6-tip.hbkpt.orig/kernel/trace/trace_ksym.c > > +++ linux-2.6-tip.hbkpt/kernel/trace/trace_ksym.c > > @@ -391,29 +391,32 @@ static enum print_line_t ksym_trace_outp > > > > ret = trace_seq_printf(s, "%-15s %-5d %-3d %-20s ", field->p_name, > > entry->pid, iter->cpu, field->ksym_name); > > - if (!ret) > > - return TRACE_TYPE_PARTIAL_LINE; > > + if (!ret) { > > + ret = TRACE_TYPE_PARTIAL_LINE; > > + goto err_ret; > > + } > > > > + ret = TRACE_TYPE_PARTIAL_LINE; > > switch (field->ksym_hbp->info.type) { > > case HW_BREAKPOINT_WRITE: > > - ret = trace_seq_printf(s, " W "); > > + if (!trace_seq_printf(s, " W ")) > > + goto err_ret; > > break; > > case HW_BREAKPOINT_RW: > > - ret = trace_seq_printf(s, " RW "); > > + if (!trace_seq_printf(s, " RW ")) > > + goto err_ret; > > break; > > default: > > - return TRACE_TYPE_PARTIAL_LINE; > > + goto err_ret; > > } > > > > - if (!ret) > > - return TRACE_TYPE_PARTIAL_LINE; > > - > > sprint_symbol(str, field->ip); > > ret = trace_seq_printf(s, "%-20s\n", str); > > - if (!ret) > > - return TRACE_TYPE_PARTIAL_LINE; > > - > > - return TRACE_TYPE_HANDLED; > > + if (ret) > > + return TRACE_TYPE_HANDLED; > > +err_ret: > > + trace_seq_printf(s, "\n"); > > + return ret; > > > As told in my email just before, TRACE_TYPE_PARTIAL_LINE > won't print a truncated line or a partial line. Instead, it > will be ignored and entirely retried later. > Then your newline will be ignored. > > ..unless we have a bug in trace.c > Yes, I see that TRACE_TYPE_PARTIAL_LINE isn't the cause but the early return that happens (without printing the \n character) because of missing data. > I'm not sure what it the origin of the concatenated printed entries > Ingo has reported. > The existing code in -tip reads like this: 397 switch (field->ksym_hbp->info.type) { 398 case HW_BREAKPOINT_WRITE: 399 ret = trace_seq_printf(s, " W "); 400 break; 401 case HW_BREAKPOINT_RW: 402 ret = trace_seq_printf(s, " RW "); 403 break; 404 default: 405 return TRACE_TYPE_PARTIAL_LINE; 406 } 407 408 if (!ret) 409 return TRACE_TYPE_PARTIAL_LINE; 410 411 sprint_symbol(str, field->ip); 412 ret = trace_seq_printf(s, "%-20s\n", str); 413 if (!ret) 414 return TRACE_TYPE_PARTIAL_LINE; 415 Si, if the control returns early at line 405 it skips the line at 412 which prints a newline character. Line 405 is executed if field->ksym_hbp->info.type is 0 which is true for an entry that is removed from the filter (e.g. echo jiffies:--- > ksym_trace_filter) and no amount of retries will help it get some new data (as it is already free-ed). > Did you reproduce it and then this patch fixed it? > Yes, it was reproduced and tested but actually it is the second patch that helps resolve this. The "trace_seq_printf(s, "\n");" isn't required at all. I will re-send a new patch to you which fixes the line concatenation and machine stall issue (after symbol removal in ksym_tracer). Thanks, K.Prasad -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/