linux-kernel - Re: [PATCH 1/9] signal: Rename send_signal send_signal

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Date:   Thu, 28 Apr 2022 12:27:11 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     "Eric W. Biederman" <ebiederm@...ssion.com>
Cc:     linux-kernel@...r.kernel.org, rjw@...ysocki.net,
        Oleg Nesterov <oleg@...hat.com>, mingo@...nel.org,
        vincent.guittot@...aro.org, dietmar.eggemann@....com,
        rostedt@...dmis.org, mgorman@...e.de, bigeasy@...utronix.de,
        Will Deacon <will@...nel.org>, tj@...nel.org,
        linux-pm@...r.kernel.org, Richard Weinberger <richard@....at>,
        Anton Ivanov <anton.ivanov@...bridgegreys.com>,
        Johannes Berg <johannes@...solutions.net>,
        linux-um@...ts.infradead.org, Chris Zankel <chris@...kel.net>,
        Max Filippov <jcmvbkbc@...il.com>,
        inux-xtensa@...ux-xtensa.org, Kees Cook <keescook@...omium.org>,
        Jann Horn <jannh@...gle.com>
Subject: Re: [PATCH 1/9] signal: Rename send_signal send_signal_locked

On Tue, Apr 26, 2022 at 05:52:03PM -0500, Eric W. Biederman wrote:
> Rename send_signal send_signal_locked and make to make
> it usable outside of signal.c.
> 
> Signed-off-by: "Eric W. Biederman" <ebiederm@...ssion.com>
> ---
>  include/linux/signal.h |  2 ++
>  kernel/signal.c        | 24 ++++++++++++------------
>  2 files changed, 14 insertions(+), 12 deletions(-)
> 
> diff --git a/include/linux/signal.h b/include/linux/signal.h
> index a6db6f2ae113..55605bdf5ce9 100644
> --- a/include/linux/signal.h
> +++ b/include/linux/signal.h
> @@ -283,6 +283,8 @@ extern int do_send_sig_info(int sig, struct kernel_siginfo *info,
>  extern int group_send_sig_info(int sig, struct kernel_siginfo *info,
>  			       struct task_struct *p, enum pid_type type);
>  extern int __group_send_sig_info(int, struct kernel_siginfo *, struct task_struct *);
> +extern int send_signal_locked(int sig, struct kernel_siginfo *info,
> +			      struct task_struct *p, enum pid_type type);
>  extern int sigprocmask(int, sigset_t *, sigset_t *);
>  extern void set_current_blocked(sigset_t *);
>  extern void __set_current_blocked(const sigset_t *);
> diff --git a/kernel/signal.c b/kernel/signal.c
> index 30cd1ca43bcd..b0403197b0ad 100644
> --- a/kernel/signal.c
> +++ b/kernel/signal.c
> @@ -1071,8 +1071,8 @@ static inline bool legacy_queue(struct sigpending *signals, int sig)
>  	return (sig < SIGRTMIN) && sigismember(&signals->signal, sig);
>  }
>  
> -static int __send_signal(int sig, struct kernel_siginfo *info, struct task_struct *t,
> -			enum pid_type type, bool force)
> +static int __send_signal_locked(int sig, struct kernel_siginfo *info,
> +				struct task_struct *t, enum pid_type type, bool force)
>  {
>  	struct sigpending *pending;
>  	struct sigqueue *q;

While there, could you please replace that assert_spin_locked() with
lockdep_assert_held(&t->sighand->siglock) ?

The distinction being that assert_spin_locked() checks if the lock is
held *by*anyone* whereas lockdep_assert_held() asserts the current
context holds the lock.  Also, the check goes away if you build without
lockdep.