linux-kernel - Re: [PATCH v5 06/10] Uprobes: Support SDT markers having reference count (semaphore)

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Message-ID: <20180703172543.GC23144@redhat.com>
Date:   Tue, 3 Jul 2018 19:25:43 +0200
From:   Oleg Nesterov <oleg@...hat.com>
To:     Ravi Bangoria <ravi.bangoria@...ux.ibm.com>
Cc:     srikar@...ux.vnet.ibm.com, rostedt@...dmis.org,
        mhiramat@...nel.org, peterz@...radead.org, mingo@...hat.com,
        acme@...nel.org, alexander.shishkin@...ux.intel.com,
        jolsa@...hat.com, namhyung@...nel.org,
        linux-kernel@...r.kernel.org, corbet@....net,
        linux-doc@...r.kernel.org, ananth@...ux.vnet.ibm.com,
        alexis.berlemont@...il.com, naveen.n.rao@...ux.vnet.ibm.com,
        linux-arm-kernel@...ts.infradead.org, linux-mips@...ux-mips.org,
        linux@...linux.org.uk, ralf@...ux-mips.org, paul.burton@...s.com
Subject: Re: [PATCH v5 06/10] Uprobes: Support SDT markers having reference
 count (semaphore)

On 07/03, Oleg Nesterov wrote:
>
> In short. There is a 1:1 relationship between uprobe_write_opcode(is_register => 1)
> and install_breakpoint(), and between uprobe_write_opcode(is_register => 0) and
> remove_breakpoint(). Whatever uprobe_write_opcode() can do if is_register == 1 can be
> done in install_breakpoint(), the same for is_register == 0 and remove_breakpont().
>
> What have I missed?

Ah. I missed the fact that uprobe_write_opcode() doesn't do update_ref_ctr() if
verify_opcode() returns false.

Now I understand what did you mean by "for each consumer". So if we move this logic
into install/remove_breakpoint as I tried to suggest, we will also need another error
code for the case when verify_opcode() returns false.

Oleg.