Re: [Bug 1030] rte_malloc() and rte_free() get stuck when used with signal handler

[Sarosh Arif <sarosh.arif@emumba.com>]

Thank you for help, I'll do it this way.

On Sat, Jun 11, 2022 at 9:25 PM Mattias Rönnblom <hofors@lysator.liu.se> wrote:
>
> On 2022-06-10 08:04, Sarosh Arif wrote:
> > On Thu, Jun 9, 2022 at 8:26 PM Stephen Hemminger
> > <stephen@networkplumber.org> wrote:
> >>
> >> On Thu, 09 Jun 2022 12:47:43 +0000
> >> bugzilla@dpdk.org wrote:
> >>
> >>> https://bugs.dpdk.org/show_bug.cgi?id=1030
> >>>
> >>>              Bug ID: 1030
> >>>             Summary: rte_malloc() and rte_free() get stuck when used with
> >>>                      signal handler
> >>>             Product: DPDK
> >>>             Version: 22.03
> >>>            Hardware: All
> >>>                  OS: Linux
> >>>              Status: UNCONFIRMED
> >>>            Severity: normal
> >>>            Priority: Normal
> >>>           Component: core
> >>>            Assignee: dev@dpdk.org
> >>>            Reporter: sarosh.arif@emumba.com
> >>>    Target Milestone: ---
> >>>
> >>> Created attachment 205
> >>>    --> https://bugs.dpdk.org/attachment.cgi?id=205&action=edit
> >>> calls rte_malloc and rte_free in the handler and main code
> >>>
> >>> I have a dpdk based application which uses rte_malloc() and rte_free()
> >>> frequently in it's main code. The general method to close the application is
> >>> though sending SIGINT. The application has a signal handler written for cleanup
> >>> purposes before closing the application. The handler also uses rte_free() to
> >>> release some of the memory during cleanup. The application gets stuck in a
> >>> deadlock.
> >>>
> >>>
> >>> Upon investigation I found out that both rte_free() and rte_malloc() use
> >>> rte_spinlock_lock() function to place a lock on heap. While this lock is placed
> >>> and the application receives SIGINT, it goes into the handler without releasing
> >>> the lock. Since the handler itself calls rte_free() which tries to acquire the
> >>> lock it gets stuck.
> >>>
> >>>
> >>> I have attached a sample application to reproduce this problem.
> >>>
> >>>
> >>> Steps to reproduce this problem:
> >>>
> >>> 1. compile the code provided in attachment with any version of dpdk
> >>> 2. run the compiled binary
> >>> 3. press ctrl+c till the prints stop
> >>>
> >>> Actual Results:
> >>> The application gets stuck in either rte_free() or rte_malloc()
> >>>
> >>> Expected Results:
> >>> Application should allocate and free the memory without getting stuck
> >>>
> >>
> >> rte_malloc and rte_free are not async sigsafe()
> >>
> > Oh, I did not know that. This should be mentioned in the documentation.
>
> Is there anything except <rte_atomic.h> that is/should be async-signal-safe?
>
> >> but then again regular glibc is not either.
> > Memory allocated with glibc malloc() is freed by itself upon closing
> > the application. My application runs as a secondary process, and it
> > needs to use rte_malloc() specifically because the memory should be
> > shared between the two processes. If I don't free it upon closure it
> > would just be leaked. Is there any other solution for it?
>
> The standard solution is that the signal handler using some appropriate,
> async-signal-safe way talks to the main thread, which then goes on to
> cleanly terminate the application.
>
> A write() to an fd, or an atomic store to a flag are two options.