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Message-Id: <20250407-improve_errseq-v1-1-7b27cbeb8298@quicinc.com>
Date: Mon, 07 Apr 2025 19:44:16 +0800
From: Zijun Hu <zijun_hu@...oud.com>
To: Andrew Morton <akpm@...ux-foundation.org>,
Jeff Layton <jlayton@...nel.org>
Cc: Zijun Hu <zijun_hu@...oud.com>, linux-kernel@...r.kernel.org,
Zijun Hu <quic_zijuhu@...cinc.com>
Subject: [PATCH] errseq: Eliminate special limitation for macro MAX_ERRNO
From: Zijun Hu <quic_zijuhu@...cinc.com>
Current errseq implementation depends on a very special precondition
that macro MAX_ERRNO must be (2^n - 1).
Eliminate the limitation by
- redefine macro ERRSEQ_SHIFT.
- define a new macro ERRNO_MASK instead of MAX_ERRNO for errno mask.
Signed-off-by: Zijun Hu <quic_zijuhu@...cinc.com>
---
lib/errseq.c | 13 +++++++------
1 file changed, 7 insertions(+), 6 deletions(-)
diff --git a/lib/errseq.c b/lib/errseq.c
index 93e9b94358dc63dcc911fd45a01ccf38d2104ecf..13a2581c5a878445f8a089d0d34e901f77a9e074 100644
--- a/lib/errseq.c
+++ b/lib/errseq.c
@@ -34,11 +34,14 @@
*/
/* The low bits are designated for error code (max of MAX_ERRNO) */
-#define ERRSEQ_SHIFT ilog2(MAX_ERRNO + 1)
+#define ERRSEQ_SHIFT (ilog2(MAX_ERRNO) + 1)
/* This bit is used as a flag to indicate whether the value has been seen */
#define ERRSEQ_SEEN (1 << ERRSEQ_SHIFT)
+/* Leverage macro ERRSEQ_SEEN to define errno mask macro here */
+#define ERRNO_MASK (ERRSEQ_SEEN - 1)
+
/* The lowest bit of the counter */
#define ERRSEQ_CTR_INC (1 << (ERRSEQ_SHIFT + 1))
@@ -60,8 +63,6 @@ errseq_t errseq_set(errseq_t *eseq, int err)
{
errseq_t cur, old;
- /* MAX_ERRNO must be able to serve as a mask */
- BUILD_BUG_ON_NOT_POWER_OF_2(MAX_ERRNO + 1);
/*
* Ensure the error code actually fits where we want it to go. If it
@@ -79,7 +80,7 @@ errseq_t errseq_set(errseq_t *eseq, int err)
errseq_t new;
/* Clear out error bits and set new error */
- new = (old & ~(MAX_ERRNO|ERRSEQ_SEEN)) | -err;
+ new = (old & ~(ERRNO_MASK | ERRSEQ_SEEN)) | -err;
/* Only increment if someone has looked at it */
if (old & ERRSEQ_SEEN)
@@ -148,7 +149,7 @@ int errseq_check(errseq_t *eseq, errseq_t since)
if (likely(cur == since))
return 0;
- return -(cur & MAX_ERRNO);
+ return -(cur & ERRNO_MASK);
}
EXPORT_SYMBOL(errseq_check);
@@ -200,7 +201,7 @@ int errseq_check_and_advance(errseq_t *eseq, errseq_t *since)
if (new != old)
cmpxchg(eseq, old, new);
*since = new;
- err = -(new & MAX_ERRNO);
+ err = -(new & ERRNO_MASK);
}
return err;
}
---
base-commit: 0af2f6be1b4281385b618cb86ad946eded089ac8
change-id: 20250407-improve_errseq-8cfa1539f9e9
Best regards,
--
Zijun Hu <quic_zijuhu@...cinc.com>
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