From: Oleg Nesterov <oleg@redhat.com>
To: Ravi Bangoria <ravi.bangoria@linux.vnet.ibm.com>
Cc: mhiramat@kernel.org, peterz@infradead.org,
srikar@linux.vnet.ibm.com, rostedt@goodmis.org, acme@kernel.org,
ananth@linux.vnet.ibm.com, akpm@linux-foundation.org,
alexander.shishkin@linux.intel.com, alexis.berlemont@gmail.com,
corbet@lwn.net, dan.j.williams@intel.com, jolsa@redhat.com,
kan.liang@intel.com, kjlx@templeofstupid.com,
kstewart@linuxfoundation.org, linux-doc@vger.kernel.org,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
milian.wolff@kdab.com, mingo@redhat.com, namhyung@kernel.org,
naveen.n.rao@linux.vnet.ibm.com, pc@us.ibm.com,
tglx@linutronix.de, yao.jin@linux.intel.com,
fengguang.wu@intel.com, jglisse@redhat.com
Subject: Re: [PATCH v2 7/9] trace_uprobe/sdt: Fix multiple update of same reference counter
Date: Tue, 10 Apr 2018 13:06:33 +0200 [thread overview]
Message-ID: <20180410110633.GA29063@redhat.com> (raw)
In-Reply-To: <84c1e60f-8aad-a0ce-59af-4fcb3f77df94@linux.vnet.ibm.com>
Hi Ravi,
On 04/10, Ravi Bangoria wrote:
>
> > and what if __mmu_notifier_register() fails simply because signal_pending() == T?
> > see mm_take_all_locks().
> >
> > at first glance this all look suspicious and sub-optimal,
>
> Yes. I should have added checks for failure cases.
> Will fix them in v3.
And what can you do if it fails? Nothing except report the problem. But
signal_pending() is not the unlikely or error condition, it should not
cause the tracing errors.
Plus mm_take_all_locks() is very heavy... BTW, uprobe_mmap_callback() is
called unconditionally. Whatever it does, can we at least move it after
the no_uprobe_events() check? Can't we also check MMF_HAS_UPROBES?
Either way, I do not feel that mmu_notifier is the right tool... Did you
consider the uprobe_clear_state() hook we already have?
Oleg.
next prev parent reply other threads:[~2018-04-10 11:06 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-04-04 8:31 [PATCH v2 0/9] trace_uprobe: Support SDT markers having reference count (semaphore) Ravi Bangoria
2018-04-04 8:31 ` [PATCH v2 1/9] Uprobe: Export vaddr <-> offset conversion functions Ravi Bangoria
2018-04-04 8:31 ` [PATCH v2 2/9] mm: Prefix vma_ to vaddr_to_offset() and offset_to_vaddr() Ravi Bangoria
2018-04-04 8:31 ` [PATCH v2 3/9] Uprobe: Move mmput() into free_map_info() Ravi Bangoria
2018-04-04 8:31 ` [PATCH v2 4/9] Uprobe: Rename map_info to uprobe_map_info Ravi Bangoria
2018-04-04 8:31 ` [PATCH v2 5/9] Uprobe: Export uprobe_map_info along with uprobe_{build/free}_map_info() Ravi Bangoria
2018-04-04 8:31 ` [PATCH v2 6/9] trace_uprobe: Support SDT markers having reference count (semaphore) Ravi Bangoria
2018-04-04 15:03 ` [RFC PATCH] trace_uprobe: trace_uprobe_mmap() can be static kbuild test robot
2018-04-04 15:03 ` [PATCH v2 6/9] trace_uprobe: Support SDT markers having reference count (semaphore) kbuild test robot
2018-04-04 8:31 ` [PATCH v2 7/9] trace_uprobe/sdt: Fix multiple update of same reference counter Ravi Bangoria
2018-04-04 13:18 ` kbuild test robot
2018-04-04 13:24 ` kbuild test robot
2018-04-09 13:17 ` Oleg Nesterov
2018-04-09 13:32 ` Ravi Bangoria
2018-04-09 13:41 ` Ravi Bangoria
2018-04-09 13:29 ` Oleg Nesterov
2018-04-10 8:19 ` Ravi Bangoria
2018-04-10 11:06 ` Oleg Nesterov [this message]
2018-04-11 4:28 ` Ravi Bangoria
2018-04-04 8:31 ` [PATCH v2 8/9] trace_uprobe/sdt: Document about " Ravi Bangoria
2018-04-04 8:31 ` [PATCH v2 9/9] perf probe: Support SDT markers having reference counter (semaphore) Ravi Bangoria
2018-04-09 7:28 ` Masami Hiramatsu
2018-04-09 8:29 ` Ravi Bangoria
2018-04-09 14:08 ` Masami Hiramatsu
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