From 76d62f24db07f22ccf9bc18ca793c27d4ebef721 Mon Sep 17 00:00:00 2001 From: John Stultz Date: Wed, 14 Dec 2022 23:18:34 +0000 Subject: pstore: Switch pmsg_lock to an rt_mutex to avoid priority inversion Wei Wang reported seeing priority inversion caused latencies caused by contention on pmsg_lock, and suggested it be switched to a rt_mutex. I was initially hesitant this would help, as the tasks in that trace all seemed to be SCHED_NORMAL, so the benefit would be limited to only nice boosting. However, another similar issue was raised where the priority inversion was seen did involve a blocked RT task so it is clear this would be helpful in that case. Cc: Wei Wang Cc: Midas Chien Cc: Connor O'Brien Cc: Kees Cook Cc: Anton Vorontsov Cc: Colin Cross Cc: Tony Luck Cc: kernel-team@android.com Fixes: 9d5438f462ab ("pstore: Add pmsg - user-space accessible pstore object") Reported-by: Wei Wang Signed-off-by: John Stultz Signed-off-by: Kees Cook Link: https://lore.kernel.org/r/20221214231834.3711880-1-jstultz@google.com --- fs/pstore/pmsg.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) (limited to 'fs/pstore') diff --git a/fs/pstore/pmsg.c b/fs/pstore/pmsg.c index d8542ec2f38c..18cf94b597e0 100644 --- a/fs/pstore/pmsg.c +++ b/fs/pstore/pmsg.c @@ -7,9 +7,10 @@ #include #include #include +#include #include "internal.h" -static DEFINE_MUTEX(pmsg_lock); +static DEFINE_RT_MUTEX(pmsg_lock); static ssize_t write_pmsg(struct file *file, const char __user *buf, size_t count, loff_t *ppos) @@ -28,9 +29,9 @@ static ssize_t write_pmsg(struct file *file, const char __user *buf, if (!access_ok(buf, count)) return -EFAULT; - mutex_lock(&pmsg_lock); + rt_mutex_lock(&pmsg_lock); ret = psinfo->write_user(&record, buf); - mutex_unlock(&pmsg_lock); + rt_mutex_unlock(&pmsg_lock); return ret ? ret : count; } -- cgit v1.2.3-58-ga151 From 2f4fec5943407318b9523f01ce1f5d668c028332 Mon Sep 17 00:00:00 2001 From: John Stultz Date: Wed, 21 Dec 2022 05:18:55 +0000 Subject: pstore: Make sure CONFIG_PSTORE_PMSG selects CONFIG_RT_MUTEXES In commit 76d62f24db07 ("pstore: Switch pmsg_lock to an rt_mutex to avoid priority inversion") I changed a lock to an rt_mutex. However, its possible that CONFIG_RT_MUTEXES is not enabled, which then results in a build failure, as the 0day bot detected: https://lore.kernel.org/linux-mm/202212211244.TwzWZD3H-lkp@intel.com/ Thus this patch changes CONFIG_PSTORE_PMSG to select CONFIG_RT_MUTEXES, which ensures the build will not fail. Cc: Wei Wang Cc: Midas Chien Cc: Connor O'Brien Cc: Kees Cook Cc: Anton Vorontsov Cc: Colin Cross Cc: Tony Luck Cc: kernel test robot Cc: kernel-team@android.com Fixes: 76d62f24db07 ("pstore: Switch pmsg_lock to an rt_mutex to avoid priority inversion") Reported-by: kernel test robot Signed-off-by: John Stultz Signed-off-by: Kees Cook Link: https://lore.kernel.org/r/20221221051855.15761-1-jstultz@google.com --- fs/pstore/Kconfig | 1 + 1 file changed, 1 insertion(+) (limited to 'fs/pstore') diff --git a/fs/pstore/Kconfig b/fs/pstore/Kconfig index 8adabde685f1..c49d554cc9ae 100644 --- a/fs/pstore/Kconfig +++ b/fs/pstore/Kconfig @@ -126,6 +126,7 @@ config PSTORE_CONSOLE config PSTORE_PMSG bool "Log user space messages" depends on PSTORE + select RT_MUTEXES help When the option is enabled, pstore will export a character interface /dev/pmsg0 to log user space messages. On reboot -- cgit v1.2.3-58-ga151 From beca3e311a49cd3c55a056096531737d7afa4361 Mon Sep 17 00:00:00 2001 From: Luca Stefani Date: Thu, 22 Dec 2022 14:10:49 +0100 Subject: pstore: Properly assign mem_type property If mem-type is specified in the device tree it would end up overriding the record_size field instead of populating mem_type. As record_size is currently parsed after the improper assignment with default size 0 it continued to work as expected regardless of the value found in the device tree. Simply changing the target field of the struct is enough to get mem-type working as expected. Fixes: 9d843e8fafc7 ("pstore: Add mem_type property DT parsing support") Cc: stable@vger.kernel.org Signed-off-by: Luca Stefani Signed-off-by: Kees Cook Link: https://lore.kernel.org/r/20221222131049.286288-1-luca@osomprivacy.com --- fs/pstore/ram.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'fs/pstore') diff --git a/fs/pstore/ram.c b/fs/pstore/ram.c index 9a5052431fd3..ade66dbe5f39 100644 --- a/fs/pstore/ram.c +++ b/fs/pstore/ram.c @@ -680,7 +680,7 @@ static int ramoops_parse_dt(struct platform_device *pdev, field = value; \ } - parse_u32("mem-type", pdata->record_size, pdata->mem_type); + parse_u32("mem-type", pdata->mem_type, pdata->mem_type); parse_u32("record-size", pdata->record_size, 0); parse_u32("console-size", pdata->console_size, 0); parse_u32("ftrace-size", pdata->ftrace_size, 0); -- cgit v1.2.3-58-ga151