Attachment 225031 Details for Bug 255947 – futex requeue patch

[patch] futex requeue patch

futex-requeue.patch (text/plain), 2.67 KB, created by pitwuu on 2021-05-17 15:13:24 UTC

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Creator: pitwuu

Created: 2021-05-17 15:13:24 UTC

Size: 2.67 KB

patch

obsolete

>diff --git a/sys/compat/linux/linux_futex.c b/sys/compat/linux/linux_futex.c
>index da1a91916869..12b244c48b9a 100644
>--- a/sys/compat/linux/linux_futex.c
>+++ b/sys/compat/linux/linux_futex.c
>@@ -664,6 +664,7 @@ linux_sys_futex(struct thread *td, struct linux_sys_futex_args *args)
> 	struct timespec uts, *ts;
> 	int error, save;
> 	uint32_t flags, val;
>+	int no_compare;
> 
> 	if (args->op & LINUX_FUTEX_PRIVATE_FLAG) {
> 		flags = 0;
>@@ -688,6 +689,7 @@ linux_sys_futex(struct thread *td, struct linux_sys_futex_args *args)
> 
> 	error = 0;
> 	f = f2 = NULL;
>+	no_compare = 0;		// for FUTEX_REQUEUE
> 
> 	switch (args->op) {
> 	case LINUX_FUTEX_WAIT:
>@@ -767,6 +769,27 @@ linux_sys_futex(struct thread *td, struct linux_sys_futex_args *args)
> 		futex_put(f, NULL);
> 		break;
> 
>+	case LINUX_FUTEX_REQUEUE:
>+		/*
>+		 * Glibc does not use this operation since version 2.3.3,
>+		 * as it is racy and replaced by FUTEX_CMP_REQUEUE operation.
>+		 * Glibc versions prior to 2.3.3 fall back to FUTEX_WAKE when
>+		 * FUTEX_REQUEUE returned EINVAL.
>+		 */
>+		pem = pem_find(td->td_proc);
>+		if ((pem->flags & LINUX_XDEPR_REQUEUEOP) == 0) {
>+			linux_msg(td, "warn: deprecated FUTEX_REQUEUE");
>+			pem->flags |= LINUX_XDEPR_REQUEUEOP;
>+			LIN_SDT_PROBE0(futex, linux_sys_futex,
>+					deprecated_requeue);
>+		}
>+		/*
>+		 * The above is true, however musl libc does make use of the
>+		 * futex requeue operation, so we add support for it.
>+		 */
>+		no_compare = 1;
>+		/* FALLTHROUGH */
>+
> 	case LINUX_FUTEX_CMP_REQUEUE:
> 		LIN_SDT_PROBE5(futex, linux_sys_futex, debug_cmp_requeue,
> 		    args->uaddr, args->val, args->val3, args->uaddr2,
>@@ -819,7 +842,7 @@ linux_sys_futex(struct thread *td, struct linux_sys_futex_args *args)
> 			    error);
> 			return (error);
> 		}
>-		if (val != args->val3) {
>+		if ((no_compare == 0) && val != args->val3) {
> 			LIN_SDT_PROBE2(futex, linux_sys_futex,
> 			    debug_cmp_requeue_value_neq, args->val, val);
> 			LINUX_CTR2(sys_futex, "CMP_REQUEUE val 0x%x != uval 0x%x",
>@@ -931,22 +954,6 @@ linux_sys_futex(struct thread *td, struct linux_sys_futex_args *args)
> 		}
> 		return (ENOSYS);
> 
>-	case LINUX_FUTEX_REQUEUE:
>-		/*
>-		 * Glibc does not use this operation since version 2.3.3,
>-		 * as it is racy and replaced by FUTEX_CMP_REQUEUE operation.
>-		 * Glibc versions prior to 2.3.3 fall back to FUTEX_WAKE when
>-		 * FUTEX_REQUEUE returned EINVAL.
>-		 */
>-		pem = pem_find(td->td_proc);
>-		if ((pem->flags & LINUX_XDEPR_REQUEUEOP) == 0) {
>-			linux_msg(td, "unsupported FUTEX_REQUEUE");
>-			pem->flags |= LINUX_XDEPR_REQUEUEOP;
>-			LIN_SDT_PROBE0(futex, linux_sys_futex,
>-			    deprecated_requeue);
>-		}
>-		return (EINVAL);
>-
> 	case LINUX_FUTEX_WAIT_REQUEUE_PI:
> 		/* not yet implemented */
> 		pem = pem_find(td->td_proc);

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Attachments on bug 255947: 225031