From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id ACA9645BF9; Wed, 13 Mar 2024 13:28:44 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1710336524; cv=none; b=Qoa4wEceRqL/8/9FrPMRECUfV7sWypiiGHNXi6YFHfjehIlVU8FQGllD+gm/EzfXhZ7hCiWRwuc8Rai/Q1kzwwkRfSB0HNHmIgfkZ7UjrFEDw6kFdvgsvj+c8lsjrHULfqKWqveDNm0auen4+RfEXo+WfkGeD+C6GqCAsaJkQno= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1710336524; c=relaxed/simple; bh=nxOroR4b2rIUnv+V/UG5lc0jC6pDP1cKjLwLqOz+xw4=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=AtRooB1ERS00008mCLxjI97D42P7fH2easJr87iIYvPLniry+PDP7gW53TH9mOJiKmIhCrhOrsKHlBDH6qzaxSIqQKznXNNWk61By4YS+diIscde4+4+MnBbWL559DmK34/4/Ivr2vxietg0k83PU/I3s/stq8Rqrtn8pFiqaWk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=TpnFdPPB; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="TpnFdPPB" Received: by smtp.kernel.org (Postfix) with ESMTPSA id DCE02C433C7; Wed, 13 Mar 2024 13:28:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1710336524; bh=nxOroR4b2rIUnv+V/UG5lc0jC6pDP1cKjLwLqOz+xw4=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=TpnFdPPBkSHLmGC5KJOHt1TJpVHGJpEea8ClPaOqKVIyFvtdhjJ0EWPHeRAhiKvY1 QZ7VYgdxAnJNIu4y8E184jdMnhX/LRfZYwS70aHgS1ycSXEI7GQ/5t2VfcerG0LqSX CceWrXXGev/8+Swu/K1Zsz2IJlBI5tVE/hdiItrknDSWg8qdKzPZiS/SEen7afHzn1 aheZRPExhuNQ9iKhKqwB5DmBckF0Igb+mDQ5ikfOmHIfQEpG0LrZaTYjxsPjG4xYF3 dg5TW+qViVGgU1SYlEzn1hbdvtSCvbUYGZB/c6cgSa4PqtPYKJIc7dB6XmvEYD3cDV EQ6u4II/Um+3Q== Date: Wed, 13 Mar 2024 10:28:41 -0300 From: Arnaldo Carvalho de Melo To: Sebastian Andrzej Siewior Cc: linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org, Adrian Hunter , Alexander Shishkin , Ian Rogers , Ingo Molnar , Jiri Olsa , Marco Elver , Mark Rutland , Namhyung Kim , Peter Zijlstra , Thomas Gleixner Subject: Re: [PATCH v2 0/4] perf: Make SIGTRAP and __perf_pending_irq() work on RT. Message-ID: References: <20240312180814.3373778-1-bigeasy@linutronix.de> <20240313081303.DClwQrvb@linutronix.de> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20240313081303.DClwQrvb@linutronix.de> On Wed, Mar 13, 2024 at 09:13:03AM +0100, Sebastian Andrzej Siewior wrote: > On 2024-03-12 18:42:38 [-0300], Arnaldo Carvalho de Melo wrote: > … > > But: > > > > [acme@nine ~]$ pidof exec_child > > 24273 24271 24270 24269 24268 24267 24266 24265 24264 24263 24262 24261 24260 24259 > … > > > [root@nine ~]# cat /proc/24263/stack > > [<0>] irqentry_exit_to_user_mode+0x1c9/0x1e0 > > [<0>] asm_sysvec_apic_timer_interrupt+0x16/0x20 > > [root@nine ~]# > … > > [acme@nine ~]$ ps ax|grep exec_child| wc -l > > 504 > > [acme@nine ~]$ ps ax|grep exec_child| tail > > 24264 pts/0 R 0:04 exec_child > > 24265 pts/0 R 0:04 exec_child > > 24266 pts/0 R 0:04 exec_child > > 24267 pts/0 R 0:04 exec_child > > 24268 pts/0 R 0:04 exec_child > > 24269 pts/0 R 0:04 exec_child > > 24270 pts/0 R 0:04 exec_child > > 24271 pts/0 R 0:04 exec_child > > 24273 pts/0 R 0:04 exec_child > > 26704 pts/1 S+ 0:00 grep --color=auto exec_child > > [acme@nine ~]$ > > > > All in 'R' state. > > > > [root@nine ~]# killall exec_child > > exec_child: no process found > > [root@nine ~]# ps ax | grep exec_child | head -5 > > 22964 pts/0 R 0:06 exec_child > > 23046 pts/0 R 0:05 exec_child > > 23128 pts/0 R 0:05 exec_child > > 23129 pts/0 R 0:05 exec_child > > 23181 pts/0 R 0:05 exec_child > > [root@nine ~]# kill 22964 23046 23128 23129 23181 > > [root@nine ~]# ps ax | grep exec_child | head -5 > > 23182 pts/0 R 0:06 exec_child > > 23196 pts/0 R 0:06 exec_child > > 23197 pts/0 R 0:06 exec_child > > 23210 pts/0 R 0:06 exec_child > > 23213 pts/0 R 0:06 exec_child > > [root@nine ~]# > You can't kill them? I can, they remain in R state and I can kill them with 'kill `pidof exec_child`' > > at the end they disappeared, on this last run. > > But if I do a 'killall remove_on_exec' and stop that loop (control+C/Z) > > we get all those exec_child running a seemingly eternal loop: > > Is this new or was it there? Is this VM or bare metal? bare metal. > One part I don't get: did you let it run or did you kill it? If I let them run they will finish and exit, no exec_child remains. If I instead try to stop the loop that goes on forking the 100 of them, then the exec_child remain spinning. > `exec_child' spins until a signal is received or the parent kills it. So > it shouldn't remain there for ever. And my guess, that it is in spinning > in userland and not in kernel. Checking that now, the stack is the one I posted: > > [root@nine ~]# cat /proc/24263/stack > > [<0>] irqentry_exit_to_user_mode+0x1c9/0x1e0 > > [<0>] asm_sysvec_apic_timer_interrupt+0x16/0x20 > > [root@nine ~]# > I tried it on bare metal and VM and couldn't reproduce this. All my tests are in bare metal. - Arnaldo