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From: Nam Cao <namcao@linutronix.de>
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To: Gabriele Monaco <gmonaco@redhat.com>, linux-kernel@vger.kernel.org,
 Steven Rostedt <rostedt@goodmis.org>, Jonathan Corbet <corbet@lwn.net>,
 Masami Hiramatsu <mhiramat@kernel.org>,
 linux-trace-kernel@vger.kernel.org, linux-doc@vger.kernel.org
Cc: Gabriele Monaco <gmonaco@redhat.com>, Tomas Glozar <tglozar@redhat.com>,
 Juri Lelli <jlelli@redhat.com>, Clark Williams <williams@redhat.com>, John
 Kacur <jkacur@redhat.com>
Subject: Re: [PATCH v2 20/20] rv: Add deadline monitors
In-Reply-To: <20250919140954.104920-21-gmonaco@redhat.com>
References: <20250919140954.104920-1-gmonaco@redhat.com>
 <20250919140954.104920-21-gmonaco@redhat.com>
Date: Fri, 10 Oct 2025 17:04:23 +0200
Message-ID: <87a51yyf0o.fsf@yellow.woof>
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Gabriele Monaco <gmonaco@redhat.com> writes:
> +/*
> + * Dummy values if not available
> + */
> +#ifndef __NR_sched_setscheduler
> +#define __NR_sched_setscheduler -1
> +#endif
> +#ifndef __NR_sched_setattr
> +#define __NR_sched_setattr -2
> +#endif

You can use __COUNTER__ intead, would make it easier to add to or remove
from this list later on.

> +static void handle_syscall(void *data, struct pt_regs *regs, long id)
> +{
> +	struct task_struct *p;
> +	int new_policy = -1;
> +
> +	new_policy = extract_params(regs, id, &p);
> +	if (new_policy < 0 || new_policy == p->policy)
> +		return;
> +	if (p->policy == SCHED_DEADLINE)
> +		da_reset(EXPAND_ID(&p->dl, DL_TASK));
> +	else if (new_policy == SCHED_DEADLINE)
> +		da_create_conditional(EXPAND_ID(&p->dl, DL_TASK), GFP_NOWAIT);
> +}

What if the syscall fails for any reason? Wouldn't the monitor stores
incorrect information?

Nam