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a=rsa-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_rsa; t=1738328798; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=2imtWDOgf4MJpp23GV2tQk70uv+/Ghez/VQziH4ELkk=; b=WhXaTUhoTWFGBxGJne2ZNMHVyI9tJ3+Dn2vqB6/EWX0TWefcoGvmjmxdKkNwEPf7SKRWzo 2A5MuqX/rQFtobzTSg+C90Pd7uW0IERqHLwQLwfEUGONwpqs8spaa2cnXaxotg6mWHtq85 i8tGaj+MoU7AKBeO6s5S9s2+OcZfhp0= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_ed25519; t=1738328798; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=2imtWDOgf4MJpp23GV2tQk70uv+/Ghez/VQziH4ELkk=; b=TIBw2m4GvUfy2hfVADBrNxhTMSH0wch4ZzrGQ/1P+TCMAFvYcfnLtmDAJebjHTe0h7D3Dm mcpcVnWjyHUJ3OBg== Date: Fri, 31 Jan 2025 14:06:38 +0100 (CET) From: Miroslav Benes To: Yafang Shao cc: Petr Mladek , jpoimboe@kernel.org, jikos@kernel.org, joe.lawrence@redhat.com, live-patching@vger.kernel.org Subject: Re: [PATCH] livepatch: Avoid hard lockup caused by klp_try_switch_task() In-Reply-To: Message-ID: References: <20250122085146.41553-1-laoar.shao@gmail.com> User-Agent: Alpine 2.21 (LSU 202 2017-01-01) Precedence: bulk X-Mailing-List: live-patching@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-Spam-Level: X-Spamd-Result: default: False [-2.80 / 50.00]; BAYES_HAM(-3.00)[99.99%]; SUSPICIOUS_RECIPS(1.50)[]; NEURAL_HAM_LONG(-1.00)[-1.000]; NEURAL_HAM_SHORT(-0.20)[-0.993]; MIME_GOOD(-0.10)[text/plain]; FREEMAIL_TO(0.00)[gmail.com]; RCVD_COUNT_ZERO(0.00)[0]; MIME_TRACE(0.00)[0:+]; TAGGED_RCPT(0.00)[]; ARC_NA(0.00)[]; MID_RHS_MATCH_FROMTLD(0.00)[]; FREEMAIL_ENVRCPT(0.00)[gmail.com]; DKIM_SIGNED(0.00)[suse.cz:s=susede2_rsa,suse.cz:s=susede2_ed25519]; FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[]; FROM_EQ_ENVFROM(0.00)[]; FUZZY_BLOCKED(0.00)[rspamd.com]; TO_MATCH_ENVRCPT_ALL(0.00)[]; RCPT_COUNT_FIVE(0.00)[6] X-Spam-Score: -2.80 X-Spam-Flag: NO Hi, > $ cat log | grep do_exit | wc -l > 1061 > > It seems that there are simply too many threads executing do_exit() at > the moment. > > > > > You might try to use printk_deferred() instead. Also you might need > > to disable interrupts around the read_lock()/read_unlock() to > > make sure that the console handling will be deferred after > > the tasklist_lock gets released. > > > > Anyway, I am against this patch. > > However, there is still a risk of triggering a hard lockup if a large > number of tasks are involved. And as Petr said, it is very likely caused by pr_debug() in this setup. The proposed patch is not a fix and would make things only worse. Regards, Miroslav