linux-kernel - [PATCH v4 2/6] driver core: Set deferred_probe_timeout to a longer default if CONFIG

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Message-Id: <20200220050440.45878-3-john.stultz@linaro.org>
Date:   Thu, 20 Feb 2020 05:04:36 +0000
From:   John Stultz <john.stultz@...aro.org>
To:     lkml <linux-kernel@...r.kernel.org>
Cc:     John Stultz <john.stultz@...aro.org>,
        Rob Herring <robh@...nel.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Kevin Hilman <khilman@...nel.org>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Pavel Machek <pavel@....cz>, Len Brown <len.brown@...el.com>,
        Todd Kjos <tkjos@...gle.com>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>,
        Thierry Reding <treding@...dia.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-pm@...r.kernel.org
Subject: [PATCH v4 2/6] driver core: Set deferred_probe_timeout to a longer default if CONFIG_MODULES is set

When using modules, its common for the modules not to be loaded
until quite late by userland. With the current code,
driver_deferred_probe_check_state() will stop returning
EPROBE_DEFER after late_initcall, which can cause module
dependency resolution to fail after that.

So allow a longer window of 30 seconds (picked somewhat
arbitrarily, but influenced by the similar regulator core
timeout value) in the case where modules are enabled.

Cc: Rob Herring <robh@...nel.org>
Cc: "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc: Kevin Hilman <khilman@...nel.org>
Cc: Ulf Hansson <ulf.hansson@...aro.org>
Cc: Pavel Machek <pavel@....cz>
Cc: Len Brown <len.brown@...el.com>
Cc: Todd Kjos <tkjos@...gle.com>
Cc: Bjorn Andersson <bjorn.andersson@...aro.org>
Cc: Liam Girdwood <lgirdwood@...il.com>
Cc: Mark Brown <broonie@...nel.org>
Cc: Thierry Reding <treding@...dia.com>
Cc: Linus Walleij <linus.walleij@...aro.org>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: linux-pm@...r.kernel.org
Signed-off-by: John Stultz <john.stultz@...aro.org>
Change-Id: I9c5a02a54915ff53f9f14d49c601f41d7105e05e
---
v4:
* Split out into its own patch as suggested by Mark
* Made change conditional on CONFIG_MODULES
---
 drivers/base/dd.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/base/dd.c b/drivers/base/dd.c
index bb383dca39c1..fa138f24e2d3 100644
--- a/drivers/base/dd.c
+++ b/drivers/base/dd.c
@@ -224,7 +224,16 @@ static int deferred_devs_show(struct seq_file *s, void *data)
 }
 DEFINE_SHOW_ATTRIBUTE(deferred_devs);
 
+#ifdef CONFIG_MODULES
+/*
+ * In the case of modules, set the default probe timeout to
+ * 30 seconds to give userland some time to load needed modules
+ */
+static int deferred_probe_timeout = 30;
+#else
+/* In the case of !modules, no probe timeout needed */
 static int deferred_probe_timeout = -1;
+#endif
 static int __init deferred_probe_timeout_setup(char *str)
 {
 	int timeout;
-- 
2.17.1