Re: [PATCH] [1/6] Add pselect/ppoll system call implementation

[Andrew Morton]

David Woodhouse <dwmw2@xxxxxxxxxxxxx> wrote:
>
> This patch adds the pselect() and ppoll() system calls, providing core
>  routines usable by the original select() and poll() system calls and
>  also the new calls (with their semantics w.r.t timeouts).

This patch sends python into a busywait:

root      2041 98.6  0.4  11192  4656 ?        R    02:36   5:29 python ./hpssd.py

strace says:

select(6, [4 5], [], [], {0, 500000})   = 0 (Timeout)
select(6, [4 5], [], [], {0, 500000})   = 0 (Timeout)
select(6, [4 5], [], [], {0, 500000})   = 0 (Timeout)
select(6, [4 5], [], [], {0, 500000})   = 0 (Timeout)
select(6, [4 5], [], [], {0, 500000})   = 0 (Timeout)
select(6, [4 5], [], [], {0, 500000})   = 0 (Timeout)
select(6, [4 5], [], [], {0, 500000})   = 0 (Timeout)
select(6, [4 5], [], [], {0, 500000})   = 0 (Timeout)
select(6, [4 5], [], [], {0, 500000})   = 0 (Timeout)
select(6, [4 5], [], [], {0, 500000})   = 0 (Timeout)
select(6, [4 5], [], [], {0, 500000})   = 0 (Timeout)
select(6, [4 5], [], [], {0, 500000})   = 0 (Timeout)
select(6, [4 5], [], [], {0, 500000})   = 0 (Timeout)
select(6, [4 5], [], [], {0, 500000})   = 0 (Timeout)
select(6, [4 5], [], [], {0, 500000})   = 0 (Timeout)
select(6, [4 5], [], [], {0, 500000})   = 0 (Timeout)
select(6, [4 5], [], [], {0, 500000})   = 0 (Timeout)
select(6, [4 5], [], [], {0, 500000})   = 0 (Timeout)
select(6, [4 5], [], [], {0, 500000})   = 0 (Timeout)


The below fixes it.

A few slipups here, so please can you re-review the code that lands in next
-mm, make sure we got everything?


--- devel/fs/select.c~add-pselect-ppoll-system-call-implementation-fix	2006-01-13 03:24:53.000000000 -0800
+++ devel-akpm/fs/select.c	2006-01-13 03:30:27.000000000 -0800
@@ -390,7 +390,7 @@ asmlinkage long sys_select(int n, fd_set
 		if ((u64)tv.tv_sec >= (u64)MAX_INT64_SECONDS)
 			timeout = -1;	/* infinite */
 		else {
-			timeout = ROUND_UP(tv.tv_sec, 1000000/HZ);
+			timeout = ROUND_UP(tv.tv_usec, USEC_PER_SEC/HZ);
 			timeout += tv.tv_sec * HZ;
 		}
 	}
@@ -441,7 +441,7 @@ asmlinkage long sys_pselect7(int n, fd_s
 		if ((u64)ts.tv_sec >= (u64)MAX_INT64_SECONDS)
 			timeout = -1;	/* infinite */
 		else {
-			timeout = ROUND_UP(ts.tv_sec, 1000000000/HZ);
+			timeout = ROUND_UP(ts.tv_nsec, NSEC_PER_SEC/HZ);
 			timeout += ts.tv_sec * HZ;
 		}
 	}
@@ -723,7 +723,7 @@ asmlinkage long sys_ppoll(struct pollfd 
 		if ((u64)ts.tv_sec >= (u64)MAX_INT64_SECONDS)
 			timeout = -1;	/* infinite */
 		else {
-			timeout = ROUND_UP(ts.tv_sec, 1000000000/HZ);
+			timeout = ROUND_UP(ts.tv_nsec, NSEC_PER_SEC/HZ);
 			timeout += ts.tv_sec * HZ;
 		}
 	}
_

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