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Mon, 17 Sep 2018 19:43:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=codeaurora.org; s=default; t=1537213427; bh=9Vd6kliHS+GxDvROhrELPpl3K9gR/Xr9YdSczQC2Np4=; h=Subject:To:Cc:References:From:Date:In-Reply-To:From; b=oPMeRMKPEizLi0RgMV10g9nadOTKmkZyuF/3XEfKLO9oIWzDd9zyi7vrbgccI3UjA eztVTSmwRTZFQuyEcEj3Di7zWqpSAIMQGf+oUpmYk3VU/ZEpicJq0jOLTM8MprM+kU tTk4N7RiqD60rORSZRntqS4xTVmokZSCiRi9kY20= DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org E2D50602A7 Authentication-Results: pdx-caf-mail.web.codeaurora.org; dmarc=none (p=none dis=none) header.from=codeaurora.org Authentication-Results: pdx-caf-mail.web.codeaurora.org; spf=none smtp.mailfrom=saiprakash.ranjan@codeaurora.org Subject: Re: [PATCH 2/6] pstore: Add event tracing support To: Stephen Boyd , Anton Vorontsov , Arnd Bergmann , Catalin Marinas , Colin Cross , Ingo Molnar , Jason Baron , Jim Cromie , Joe Perches , Joel Fernandes , Kees Cook , Laura Abbott , Masami Hiramatsu , Rob Herring , Steven Rostedt , Tony Luck , Will Deacon , devicetree@vger.kernel.org Cc: Rajendra Nayak , Vivek Gautam , Sibi Sankar , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org, Greg Kroah-Hartman , Ingo Molnar , Tom Zanussi , Prasad Sodagudi , tsoni@codeaurora.org, Bryan Huntsman , Tingwei Zhang References: <444d7b13-2653-ba0e-e9e6-a448fded2a77@codeaurora.org> <153720590027.119890.15984895820368075914@swboyd.mtv.corp.google.com> From: Sai Prakash Ranjan Message-ID: <03d47d84-a237-a94e-04ee-4447d8620697@codeaurora.org> Date: Tue, 18 Sep 2018 01:13:30 +0530 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <153720590027.119890.15984895820368075914@swboyd.mtv.corp.google.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 9/17/2018 11:08 PM, Stephen Boyd wrote: > Quoting Sai Prakash Ranjan (2018-09-11 03:46:01) >> On 9/9/2018 1:57 AM, Sai Prakash Ranjan wrote: >>> +void notrace pstore_event_call(struct trace_event_buffer *fbuffer) >>> +{ >>> + struct trace_iterator *iter; >>> + struct trace_seq *s; >>> + struct trace_event_call *event_call; >>> + struct pstore_record record; >>> + struct trace_event *event; >>> + struct seq_buf *seq; >>> + unsigned long flags; >>> + >>> + if (!psinfo) >>> + return; >>> + >>> + if (unlikely(oops_in_progress)) >>> + return; >>> + >>> + pstore_record_init(&record, psinfo); >>> + record.type = PSTORE_TYPE_EVENT; >>> + >>> + iter = kmalloc(sizeof(*iter), GFP_KERNEL); >>> + if (!iter) >>> + return; >>> + >>> + event_call = fbuffer->trace_file->event_call; >>> + if (!event_call || !event_call->event.funcs || >>> + !event_call->event.funcs->trace) >>> + goto fail_event; >>> + >>> + event = &fbuffer->trace_file->event_call->event; >>> + >>> + spin_lock_irqsave(&psinfo->buf_lock, flags); >>> + >>> + trace_seq_init(&iter->seq); >>> + iter->ent = fbuffer->entry; >>> + event_call->event.funcs->trace(iter, 0, event); >>> + trace_seq_putc(&iter->seq, 0); >>> + >>> + if (seq->size > psinfo->bufsize) >>> + seq->size = psinfo->bufsize; >>> + >>> + s = &iter->seq; >>> + seq = &s->seq; >>> + >>> + record.buf = (char *)(seq->buffer); >>> + record.size = seq->len; >>> + psinfo->write(&record); >>> + >>> + spin_unlock_irqrestore(&psinfo->buf_lock, flags); >>> + >>> +fail_event: >>> + kfree(iter); >>> +} >>> + >>> >> >> When tracing sched events on sdm845 mtp, I hit below bug repeatedly. >> Seems like pstore_event_call can be called in atomic context. >> I will respin the below fix in next version of the patch. >> Reviews on other parts would be appreciated, thanks. >> >> diff --git a/fs/pstore/ftrace.c b/fs/pstore/ftrace.c >> index d47dc93ac098..a497cf782ee8 100644 >> --- a/fs/pstore/ftrace.c >> +++ b/fs/pstore/ftrace.c >> @@ -73,6 +73,7 @@ void notrace pstore_event_call(struct >> trace_event_buffer *fbuffer) >> struct trace_event *event; >> struct seq_buf *seq; >> unsigned long flags; >> + gfp_t gfpflags; >> >> if (!psinfo) >> return; >> @@ -83,7 +84,9 @@ void notrace pstore_event_call(struct >> trace_event_buffer *fbuffer) >> pstore_record_init(&record, psinfo); >> record.type = PSTORE_TYPE_EVENT; >> >> - iter = kmalloc(sizeof(*iter), GFP_KERNEL); >> + gfpflags = (in_atomic() || irqs_disabled()) ? GFP_ATOMIC : >> GFP_KERNEL; >> + > Hi Stephen Thanks for the comments. > Do you need to allocate at all? Can you throw the iter on the stack? > Yes since we need to copy the contents to pstore buffer. > Using in_atomic() and irqs_disabled() to figure out if an atomic or a > non-atomic allocation should be used is not a good solution. > I took reference from a similar use by graph_trace_open() which can be called in atomic context via ftrace_dump(). I am open to correct this if there is some other way. Sai -- QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation