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[124.209.188.1]) by smtp.gmail.com with ESMTPSA id c3-20020a170902aa4300b0019f2a7f4d16sm506889plr.39.2023.03.30.21.11.56 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 30 Mar 2023 21:12:00 -0700 (PDT) Date: Fri, 31 Mar 2023 13:11:54 +0900 From: Sergey Senozhatsky To: Luis Chamberlain Cc: Linus Torvalds , Peter Zijlstra , Petr Mladek , Sergey Senozhatsky , david@redhat.com, patches@lists.linux.dev, linux-modules@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, petr.pavlu@suse.com, prarit@redhat.com, gregkh@linuxfoundation.org, rafael@kernel.org, christophe.leroy@csgroup.eu, tglx@linutronix.de, song@kernel.org, rppt@kernel.org, willy@infradead.org, vbabka@suse.cz, mhocko@suse.com, dave.hansen@linux.intel.com Subject: Re: [PATCH 4/7] sempahore: add a helper for a concurrency limiter Message-ID: <20230331041154.GC12892@google.com> References: <20230329053149.3976378-1-mcgrof@kernel.org> <20230329053149.3976378-5-mcgrof@kernel.org> <20230329072112.GG4253@hirez.programming.kicks-ass.net> <20230329091935.GP4253@hirez.programming.kicks-ass.net> <20230330115626.GA124812@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: On (23/03/30 20:45), Luis Chamberlain wrote: [..] > -static DEFINE_SEMAPHORE(console_sem); > +static DEFINE_MUTEX(console_sem); > HLIST_HEAD(console_list); > EXPORT_SYMBOL_GPL(console_list); > DEFINE_STATIC_SRCU(console_srcu); > @@ -309,7 +309,7 @@ EXPORT_SYMBOL(console_srcu_read_unlock); > * macros instead of functions so that _RET_IP_ contains useful information. > */ > #define down_console_sem() do { \ > - down(&console_sem);\ > + mutex_lock(&console_sem);\ > mutex_acquire(&console_lock_dep_map, 0, 0, _RET_IP_);\ > } while (0) > > @@ -324,7 +324,7 @@ static int __down_trylock_console_sem(unsigned long ip) > * deadlock in printk()->down_trylock_console_sem() otherwise. > */ > printk_safe_enter_irqsave(flags); > - lock_failed = down_trylock(&console_sem); > + lock_failed = !mutex_trylock(&console_sem); > printk_safe_exit_irqrestore(flags); > > if (lock_failed) > @@ -341,7 +341,7 @@ static void __up_console_sem(unsigned long ip) > mutex_release(&console_lock_dep_map, ip); > > printk_safe_enter_irqsave(flags); > - up(&console_sem); > + mutex_unlock(&console_sem); mutex_unlock() does not like when its called from IRQ, so this is not going to work very well.