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Mon, 01 Apr 2019 19:14:23 -0700 (PDT) Received: from localhost ([175.223.14.1]) by smtp.gmail.com with ESMTPSA id e4sm3169271pfh.146.2019.04.01.19.14.22 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Mon, 01 Apr 2019 19:14:22 -0700 (PDT) Date: Tue, 2 Apr 2019 11:14:19 +0900 From: Sergey Senozhatsky To: Feng Tang Cc: Andrew Morton , Petr Mladek , Steven Rostedt , Sergey Senozhatsky , linux-kernel@vger.kernel.org, Kees Cook , Borislav Petkov Subject: Re: [PATCH 1/2] printk: Add an option to flush all messages on panic Message-ID: <20190402021419.GA617@jagdpanzerIV> References: <1554115684-26846-1-git-send-email-feng.tang@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1554115684-26846-1-git-send-email-feng.tang@intel.com> User-Agent: Mutt/1.11.4 (2019-03-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On (04/01/19 18:48), Feng Tang wrote: > diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c > index 1fd45a8..58d9580 100644 > --- a/arch/powerpc/kernel/traps.c > +++ b/arch/powerpc/kernel/traps.c > @@ -179,7 +179,7 @@ extern void panic_flush_kmsg_end(void) > kmsg_dump(KMSG_DUMP_PANIC); > bust_spinlocks(0); > debug_locks_off(); > - console_flush_on_panic(); > + console_flush_on_panic(false); > } [..] > @@ -277,7 +277,7 @@ void panic(const char *fmt, ...) > * panic() is not being callled from OOPS. > */ > debug_locks_off(); > - console_flush_on_panic(); > + console_flush_on_panic(false); [..] > -void console_flush_on_panic(void) > +void console_flush_on_panic(bool flush_all) > { > /* > * If someone else is holding the console lock, trylock will fail > @@ -2539,6 +2540,12 @@ void console_flush_on_panic(void) > */ > console_trylock(); > console_may_schedule = 0; > + > + /* User may want to see all the printk messages on panic */ > + if (flush_all) { > + console_seq = log_first_seq; > + console_idx = log_first_idx; > + } > console_unlock(); So my first thought was - let's not add a `bool flag', but instead add an `enum' with clear flag names, e.g. DUMP_ALL/DUMP_PENDING, etc. Something similar to what ftrace_dump(DUMP_ALL) does. And we already have panic_print bit-mask and panic_print_sys_info(), which controls what we print when in panic. So we can move console_flush_on_panic() to panic_print_sys_info() and handle different types of console_flush_on_panic() there: --- diff --git a/kernel/panic.c b/kernel/panic.c index 0ae0d7332f12..e142faaebbcd 100644 --- a/kernel/panic.c +++ b/kernel/panic.c @@ -134,6 +134,11 @@ EXPORT_SYMBOL(nmi_panic); static void panic_print_sys_info(void) { + if (panic_print & PANIC_PRINT_REPLAY_LOGBUF) + console_flush_on_panic(DUMP_ALL); + else + console_flush_on_panic(DUMP_PENDING); + if (panic_print & PANIC_PRINT_TASK_INFO) show_state(); @@ -277,7 +282,6 @@ void panic(const char *fmt, ...) * panic() is not being callled from OOPS. */ debug_locks_off(); - console_flush_on_panic(); panic_print_sys_info(); --- After looking at this more - DUMP_ALL/DUMP_PENDING clearly depend on panic_print. So... May be we can move panic_print_sys_info() to printk.c, and for PANIC_PRINT_REPLAY_LOGBUF case just reset console seq/idx (console seq/idx are internal to printk) before we flush_on_panic. This way we would not need to modify console_flush_on_panic() prototype at all. Let's hear from people. -ss