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| author | Conrad Meyer <cem@FreeBSD.org> | 2019-08-07 19:23:07 +0000 |
|---|---|---|
| committer | Conrad Meyer <cem@FreeBSD.org> | 2019-08-07 19:23:07 +0000 |
| commit | 71db411eb627601a5f9a3464f88d75741927ce60 (patch) | |
| tree | 5d8502ef6a3f77d7a07d6353221adb9872310040 /sys | |
| parent | 29bf090e15533714696dc0eb8c3fe5550e89c569 (diff) | |
| download | src-71db411eb627601a5f9a3464f88d75741927ce60.tar.gz src-71db411eb627601a5f9a3464f88d75741927ce60.zip | |
sbuf(9): Add NOWAIT dynamic buffer extension mode
The goal is to avoid some kinds of low-memory deadlock when formatting
heap-allocated buffers.
Reviewed by: vangyzen
Sponsored by: Dell EMC Isilon
Differential Revision: https://reviews.freebsd.org/D21015
Notes
Notes:
svn path=/head/; revision=350691
Diffstat (limited to 'sys')
| -rw-r--r-- | sys/kern/subr_sbuf.c | 16 | ||||
| -rw-r--r-- | sys/sys/sbuf.h | 1 |
2 files changed, 10 insertions, 7 deletions
diff --git a/sys/kern/subr_sbuf.c b/sys/kern/subr_sbuf.c index 8fba9710debc..c94657ca97a2 100644 --- a/sys/kern/subr_sbuf.c +++ b/sys/kern/subr_sbuf.c @@ -56,11 +56,11 @@ __FBSDID("$FreeBSD$"); #ifdef _KERNEL static MALLOC_DEFINE(M_SBUF, "sbuf", "string buffers"); -#define SBMALLOC(size) malloc(size, M_SBUF, M_WAITOK|M_ZERO) +#define SBMALLOC(size, flags) malloc(size, M_SBUF, (flags) | M_ZERO) #define SBFREE(buf) free(buf, M_SBUF) #else /* _KERNEL */ #define KASSERT(e, m) -#define SBMALLOC(size) calloc(1, size) +#define SBMALLOC(size, flags) calloc(1, size) #define SBFREE(buf) free(buf) #endif /* _KERNEL */ @@ -77,6 +77,8 @@ static MALLOC_DEFINE(M_SBUF, "sbuf", "string buffers"); #define SBUF_NULINCLUDED(s) ((s)->s_flags & SBUF_INCLUDENUL) #define SBUF_ISDRAINTOEOR(s) ((s)->s_flags & SBUF_DRAINTOEOR) #define SBUF_DODRAINTOEOR(s) (SBUF_ISSECTION(s) && SBUF_ISDRAINTOEOR(s)) +#define SBUF_MALLOCFLAG(s) \ + (((s)->s_flags & SBUF_NOWAIT) ? M_NOWAIT : M_WAITOK) /* * Set / clear flags @@ -171,7 +173,7 @@ sbuf_extend(struct sbuf *s, int addlen) if (!SBUF_CANEXTEND(s)) return (-1); newsize = sbuf_extendsize(s->s_size + addlen); - newbuf = SBMALLOC(newsize); + newbuf = SBMALLOC(newsize, SBUF_MALLOCFLAG(s)); if (newbuf == NULL) return (-1); memcpy(newbuf, s->s_buf, s->s_size); @@ -198,7 +200,7 @@ sbuf_newbuf(struct sbuf *s, char *buf, int length, int flags) s->s_size = length; s->s_buf = buf; - if ((s->s_flags & SBUF_AUTOEXTEND) == 0) { + if (!SBUF_CANEXTEND(s)) { KASSERT(s->s_size >= SBUF_MINSIZE, ("attempt to create an sbuf smaller than %d bytes", SBUF_MINSIZE)); @@ -207,10 +209,10 @@ sbuf_newbuf(struct sbuf *s, char *buf, int length, int flags) if (s->s_buf != NULL) return (s); - if ((flags & SBUF_AUTOEXTEND) != 0) + if (SBUF_CANEXTEND(s)) s->s_size = sbuf_extendsize(s->s_size); - s->s_buf = SBMALLOC(s->s_size); + s->s_buf = SBMALLOC(s->s_size, SBUF_MALLOCFLAG(s)); if (s->s_buf == NULL) return (NULL); SBUF_SETFLAG(s, SBUF_DYNAMIC); @@ -235,7 +237,7 @@ sbuf_new(struct sbuf *s, char *buf, int length, int flags) if (s != NULL) return (sbuf_newbuf(s, buf, length, flags)); - s = SBMALLOC(sizeof(*s)); + s = SBMALLOC(sizeof(*s), (flags & SBUF_NOWAIT) ? M_NOWAIT : M_WAITOK); if (s == NULL) return (NULL); if (sbuf_newbuf(s, buf, length, flags) == NULL) { diff --git a/sys/sys/sbuf.h b/sys/sys/sbuf.h index 4010f3b7d31c..3b099fe3f512 100644 --- a/sys/sys/sbuf.h +++ b/sys/sys/sbuf.h @@ -52,6 +52,7 @@ struct sbuf { #define SBUF_AUTOEXTEND 0x00000001 /* automatically extend buffer */ #define SBUF_INCLUDENUL 0x00000002 /* nulterm byte is counted in len */ #define SBUF_DRAINTOEOR 0x00000004 /* use section 0 as drain EOR marker */ +#define SBUF_NOWAIT 0x00000008 /* Extend with non-blocking malloc */ #define SBUF_USRFLAGMSK 0x0000ffff /* mask of flags the user may specify */ #define SBUF_DYNAMIC 0x00010000 /* s_buf must be freed */ #define SBUF_FINISHED 0x00020000 /* set by sbuf_finish() */ |