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Thu, 28 Jan 2021 11:37:20 -0500 Received: from mail-wr1-x429.google.com (mail-wr1-x429.google.com [IPv6:2a00:1450:4864:20::429]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 17E3BC061756; Thu, 28 Jan 2021 08:36:39 -0800 (PST) Received: by mail-wr1-x429.google.com with SMTP id m13so6040310wro.12; Thu, 28 Jan 2021 08:36:39 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=J2pSAMeacjhYY4VRhMqQHxTTL1fklZ6z+iWFWs9oc44=; b=DfyF+mGipz5IdxF0ZOYjV1X5y0NhM+SOJq5KMmh/tOITvOfGsVqH7mnosOyCJImEZd FtBe1YewLQdbLECZtW/y9+LdRAzEKft/cvY+VcT2aa3dYM9QGb+Y9Ug/tuNe8kTsQ4G6 4OENy1oWjIETJvqYS+t3BZhEx9hK+mtD1RChRRV7z1uXewJcUJwuan6e2AmcKLfUaPEp YpnfAr4m15Xk9hO/dpbw1yHiIkPKA3P4zBfCjIjwaohZkcv4f3Lf/PwULvA8kkdhHFWt AyjECcPpT6pYecRegWNU+T/M1VkQrxl5I3N4yEtazuUBjfixPBvspwgEYB/T1H1GMNKe KYsA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=J2pSAMeacjhYY4VRhMqQHxTTL1fklZ6z+iWFWs9oc44=; b=CnHqY0UeM7zGZX69E5drSKHZd4hYSkB86J0FDYOtsI4f6Fl0BGUWzduyRtGUpszIT4 tDV33twz3OYModXPaLniDV7QNbocSJuyvkt+324JAWCHvjgJ++6nnSSeUu5ltf1H3PIF hr17q1rrGKjVTSaeqVuVrPTzT+V38VJNUPP3wM1NddWA3TcMrokbM3Iw6SvbEvz50rPE zsVmQW8Sh/C16P9aaQ6RaDRjdN6BWclf8hW+thYxRhZU5UT1K1TWT3UqlKuxQqxZaBeu dUqZnbuzMua/QJ1VC3k0keSmhooltH6rRX+BiSicp6Omw+AOvsr+DC3Bk6QgXPg+4+q1 Bwyg== X-Gm-Message-State: AOAM5307tWHGNDVumesW373sabuDdgBTvfXmIfYtVmjPrzC+frir4LbR oqBo/THkmh4jSxz3KDG+Q5E0wPoTY8ytW5tWMfPr9i2GePE= X-Google-Smtp-Source: ABdhPJzjtBIb9f3OwWrVVcmu1w4hFEFvKvi6v9SGkeHvpkhMmefwW5PwFRm8PwjbmSGh1qpzbdv0JI+bmeA6hVyKa/w= X-Received: by 2002:adf:dd07:: with SMTP id a7mr17587399wrm.83.1611851797734; Thu, 28 Jan 2021 08:36:37 -0800 (PST) MIME-Version: 1.0 References: <20210125234901.2730699-1-swboyd@chromium.org> In-Reply-To: <20210125234901.2730699-1-swboyd@chromium.org> From: Rob Clark Date: Thu, 28 Jan 2021 08:39:12 -0800 Message-ID: Subject: Re: [PATCH] drm/msm/kms: Make a lock_class_key for each crtc mutex To: Stephen Boyd Cc: Linux Kernel Mailing List , linux-arm-msm , freedreno , dri-devel , Krishna Manikandan Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-arm-msm@vger.kernel.org On Mon, Jan 25, 2021 at 3:49 PM Stephen Boyd wrote: > > Lockdep complains about an AA deadlock when rebooting the device. > > ============================================ > WARNING: possible recursive locking detected > 5.4.91 #1 Not tainted > -------------------------------------------- > reboot/5213 is trying to acquire lock: > ffffff80d13391b0 (&kms->commit_lock[i]){+.+.}, at: lock_crtcs+0x60/0xa4 > > but task is already holding lock: > ffffff80d1339110 (&kms->commit_lock[i]){+.+.}, at: lock_crtcs+0x60/0xa4 > > other info that might help us debug this: > Possible unsafe locking scenario: > > CPU0 > ---- > lock(&kms->commit_lock[i]); > lock(&kms->commit_lock[i]); > > *** DEADLOCK *** > > May be due to missing lock nesting notation > > 6 locks held by reboot/5213: > __arm64_sys_reboot+0x148/0x2a0 > device_shutdown+0x10c/0x2c4 > drm_atomic_helper_shutdown+0x48/0xfc > modeset_lock+0x120/0x24c > lock_crtcs+0x60/0xa4 > > stack backtrace: > CPU: 4 PID: 5213 Comm: reboot Not tainted 5.4.91 #1 > Hardware name: Google Pompom (rev1) with LTE (DT) > Call trace: > dump_backtrace+0x0/0x1dc > show_stack+0x24/0x30 > dump_stack+0xfc/0x1a8 > __lock_acquire+0xcd0/0x22b8 > lock_acquire+0x1ec/0x240 > __mutex_lock_common+0xe0/0xc84 > mutex_lock_nested+0x48/0x58 > lock_crtcs+0x60/0xa4 > msm_atomic_commit_tail+0x348/0x570 > commit_tail+0xdc/0x178 > drm_atomic_helper_commit+0x160/0x168 > drm_atomic_commit+0x68/0x80 > > This is because lockdep thinks all the locks taken in lock_crtcs() are > the same lock, when they actually aren't. That's because we call > mutex_init() in msm_kms_init() and that assigns on static key for every nit, s/on/one/ ? BR, -R > lock initialized in this loop. Let's allocate a dynamic number of > lock_class_keys and assign them to each lock so that lockdep can figure > out an AA deadlock isn't possible here. > > Fixes: b3d91800d9ac ("drm/msm: Fix race condition in msm driver with async layer updates") > Cc: Krishna Manikandan > Signed-off-by: Stephen Boyd > --- > drivers/gpu/drm/msm/msm_kms.h | 8 ++++++-- > 1 file changed, 6 insertions(+), 2 deletions(-) > > diff --git a/drivers/gpu/drm/msm/msm_kms.h b/drivers/gpu/drm/msm/msm_kms.h > index d8151a89e163..4735251a394d 100644 > --- a/drivers/gpu/drm/msm/msm_kms.h > +++ b/drivers/gpu/drm/msm/msm_kms.h > @@ -157,6 +157,7 @@ struct msm_kms { > * from the crtc's pending_timer close to end of the frame: > */ > struct mutex commit_lock[MAX_CRTCS]; > + struct lock_class_key commit_lock_keys[MAX_CRTCS]; > unsigned pending_crtc_mask; > struct msm_pending_timer pending_timers[MAX_CRTCS]; > }; > @@ -166,8 +167,11 @@ static inline int msm_kms_init(struct msm_kms *kms, > { > unsigned i, ret; > > - for (i = 0; i < ARRAY_SIZE(kms->commit_lock); i++) > - mutex_init(&kms->commit_lock[i]); > + for (i = 0; i < ARRAY_SIZE(kms->commit_lock); i++) { > + lockdep_register_key(&kms->commit_lock_keys[i]); > + __mutex_init(&kms->commit_lock[i], "&kms->commit_lock[i]", > + &kms->commit_lock_keys[i]); > + } > > kms->funcs = funcs; > > > base-commit: 19c329f6808995b142b3966301f217c831e7cf31 > -- > https://chromeos.dev >