linux-kernel - Re: [PATCH] perf_events: fix event scheduling issues introduced by transactional API (take 2)

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <AANLkTikZFOVLVIr51D_R8hB2glXp9M70QvQLx0-zKaWO@mail.gmail.com>
Date:	Wed, 26 May 2010 08:58:14 +0200
From:	Stephane Eranian <eranian@...gle.com>
To:	Lin Ming <ming.m.lin@...el.com>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	"eranian@...il.com" <eranian@...il.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"mingo@...e.hu" <mingo@...e.hu>,
	"paulus@...ba.org" <paulus@...ba.org>,
	"davem@...emloft.net" <davem@...emloft.net>,
	"fweisbec@...il.com" <fweisbec@...il.com>,
	"acme@...radead.org" <acme@...radead.org>,
	"perfmon2-devel@...ts.sf.net" <perfmon2-devel@...ts.sf.net>
Subject: Re: [PATCH] perf_events: fix event scheduling issues introduced by 
	transactional API (take 2)

On Wed, May 26, 2010 at 8:34 AM, Lin Ming <ming.m.lin@...el.com> wrote:
> On Tue, 2010-05-25 at 23:32 +0800, Peter Zijlstra wrote:
>> On Tue, 2010-05-25 at 17:02 +0200, Stephane Eranian wrote:
>> > Ok, the patch look good expect it needs:
>> >
>> > static int x86_pmu_commit_txn(const struct pmu *pmu)
>> > {
>> >         ......
>> >         /*
>> >          * copy new assignment, now we know it is possible
>> >          * will be used by hw_perf_enable()
>> >          */
>> >         memcpy(cpuc->assign, assign, n*sizeof(int));
>> >
>> >         cpuc->n_txn = 0;
>> >
>> >         return 0;
>> > }
>> >
>> > Because you always call cancel_txn() even when commit()
>> > succeeds. I don't really understand why. I think it could be
>> > avoided by clearing the group_flag in commit_txn() if it
>> > succeeds. It would also make the logical flow more natural. Why
>> > cancel something that has succeeded. You cancel when you fail/abort.
>>
>> Gah, I forgot about that. I think I suggested to Lin to do that and then
>> promptly forgot.
>
> cancel_txn() clears the transaction flag, so it is needed after both
> success and fail transaction, although the function name is a bit
> misleading.
>
> Peter's patch adds the clear of transaction flag into each
> implementation of ->commit_txn.
>
> So cancel_txn() is only called after fail transaction now.
>
Yes and I think it is less prone to confusion now.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/