+ sys_info-add-helper-for-callers-that-print-some-sys_info-on-their-own.patch added to mm-hotfixes-unstable branch

+ sys_info-add-helper-for-callers-that-print-some-sys_info-on-their-own.patch added to mm-hotfixes-unstable branch

[Andrew Morton]

The patch titled
     Subject: sys_info: add helper for callers that print some sys_info on their own
has been added to the -mm mm-hotfixes-unstable branch.  Its filename is
     sys_info-add-helper-for-callers-that-print-some-sys_info-on-their-own.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/sys_info-add-helper-for-callers-that-print-some-sys_info-on-their-own.patch

This patch will later appear in the mm-hotfixes-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Bradley Morgan <include@grrlz.net>
Subject: sys_info: add helper for callers that print some sys_info on their own
Date: Thu, 25 Jun 2026 15:25:55 +0000

Patch series "sys_info: prevent duplicate backtraces", v3.

Some callers handle SYS_INFO_ALL_BT themselves before calling sys_info().
When they strip that bit, an all_bt-only mask becomes zero and sys_info(0)
falls back to kernel_si_mask, potentially duplicating output.

This series adds sys_info_with_filter() to filter specific bits without
triggering the kernel_si_mask fallback.


This patch (of 4):

Some callers print some sys_info on their own before calling sys_info().

Add a helper which would allow to prevent a duplicated output.

It is a bit tricky because kernel_si_mask should be used only when the
call-specific si_mask is empty.  But the duplicated output must be
prevented there as well.

Link: https://lore.kernel.org/20260625152558.7450-1-include@grrlz.net
Link: https://lore.kernel.org/20260625152558.7450-2-include@grrlz.net
Fixes: a9af76a78760 ("watchdog: add sys_info sysctls to dump sys info on system lockup")
Signed-off-by: Bradley Morgan <include@grrlz.net>
Suggested-by: Petr Mladek <pmladek@suse.com>
Cc: Doug Anderson <dianders@chromium.org>
Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 include/linux/sys_info.h |    1 +
 lib/sys_info.c           |   20 ++++++++++++++++++--
 2 files changed, 19 insertions(+), 2 deletions(-)

--- a/include/linux/sys_info.h~sys_info-add-helper-for-callers-that-print-some-sys_info-on-their-own
+++ a/include/linux/sys_info.h
@@ -18,6 +18,7 @@
 #define SYS_INFO_BLOCKED_TASKS		0x00000080
 
 void sys_info(unsigned long si_mask);
+void sys_info_with_filter(unsigned long si_mask, unsigned long si_ignore_mask);
 unsigned long sys_info_parse_param(char *str);
 
 #ifdef CONFIG_SYSCTL
--- a/lib/sys_info.c~sys_info-add-helper-for-callers-that-print-some-sys_info-on-their-own
+++ a/lib/sys_info.c
@@ -136,8 +136,10 @@ static int __init sys_info_sysctl_init(v
 subsys_initcall(sys_info_sysctl_init);
 #endif
 
-static void __sys_info(unsigned long si_mask)
+static void __sys_info(unsigned long si_mask, unsigned long si_ignore_mask)
 {
+	si_mask &= ~si_ignore_mask;
+
 	if (si_mask & SYS_INFO_TASKS)
 		show_state();
 
@@ -160,7 +162,21 @@ static void __sys_info(unsigned long si_
 		show_state_filter(TASK_UNINTERRUPTIBLE);
 }
 
+void sys_info_with_filter(unsigned long si_mask, unsigned long si_ignore_mask)
+{
+	unsigned long dump_mask = si_mask & ~si_ignore_mask;
+
+	/*
+	 * Do not fall back to kernel_si_mask when the caller context
+	 * required only the ignored information.
+	 */
+	if (si_mask && !dump_mask)
+		return;
+
+	__sys_info(dump_mask ? : kernel_si_mask, si_ignore_mask);
+}
+
 void sys_info(unsigned long si_mask)
 {
-	__sys_info(si_mask ? : kernel_si_mask);
+	sys_info_with_filter(si_mask, 0);
 }
_

Patches currently in -mm which might be from include@grrlz.net are

sys_info-add-helper-for-callers-that-print-some-sys_info-on-their-own.patch
watchdog-use-sys_info_with_filter-to-avoid-duplicate-backtraces.patch
powerpc-watchdog-use-sys_info_with_filter-to-avoid-duplicate-backtraces.patch
panic-use-sys_info_with_filter-to-avoid-duplicate-backtraces.patch
lib-string-fix-memchr_inv-for-large-ranges.patch