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From: Corinna Vinschen <corinna@sourceware.org> To: cygwin-cvs@sourceware.org Subject: [newlib-cygwin] Cygwin: mmap: use SRWLOCK instead of muto Date: Wed, 24 Aug 2022 09:20:46 +0000 (GMT) [thread overview] Message-ID: <20220824092046.9F5B0385AC19@sourceware.org> (raw) https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=ee54cabad9c9fcc45275551dae7bd9fc9da78f83 commit ee54cabad9c9fcc45275551dae7bd9fc9da78f83 Author: Corinna Vinschen <corinna@vinschen.de> Date: Tue Aug 23 11:14:12 2022 +0200 Cygwin: mmap: use SRWLOCK instead of muto To reduce thread contention, use reader/writer locks as required. Signed-off-by: Corinna Vinschen <corinna@vinschen.de> Diff: --- winsup/cygwin/mm/mmap.cc | 39 +++++++++++++++++++++------------------ 1 file changed, 21 insertions(+), 18 deletions(-) diff --git a/winsup/cygwin/mm/mmap.cc b/winsup/cygwin/mm/mmap.cc index c33342bc3..332c015a7 100644 --- a/winsup/cygwin/mm/mmap.cc +++ b/winsup/cygwin/mm/mmap.cc @@ -48,9 +48,11 @@ details. */ static fhandler_dev_zero fh_anonymous; /* Used for thread synchronization while accessing mmap bookkeeping lists. */ -static NO_COPY muto mmap_guard; -#define LIST_LOCK() (mmap_guard.init ("mmap_guard")->acquire ()) -#define LIST_UNLOCK() (mmap_guard.release ()) +static NO_COPY SRWLOCK mmap_lock = SRWLOCK_INIT; +#define LIST_WRITE_LOCK() (AcquireSRWLockExclusive (&mmap_lock)) +#define LIST_WRITE_UNLOCK() (ReleaseSRWLockExclusive (&mmap_lock)) +#define LIST_READ_LOCK() (AcquireSRWLockShared (&mmap_lock)) +#define LIST_READ_UNLOCK() (ReleaseSRWLockShared (&mmap_lock)) /* Small helpers to avoid having lots of flag bit tests in the code. */ static inline bool @@ -703,12 +705,12 @@ is_mmapped_region (caddr_t start_addr, caddr_t end_address) { size_t len = end_address - start_addr; - LIST_LOCK (); + LIST_READ_LOCK (); mmap_list *map_list = mmapped_areas.get_list_by_fd (-1, NULL); if (!map_list) { - LIST_UNLOCK (); + LIST_READ_UNLOCK (); return false; } @@ -725,7 +727,7 @@ is_mmapped_region (caddr_t start_addr, caddr_t end_address) break; } } - LIST_UNLOCK (); + LIST_READ_UNLOCK (); return ret; } @@ -753,7 +755,7 @@ mmap_is_attached_or_noreserve (void *addr, size_t len) { mmap_region_status ret = MMAP_NONE; - LIST_LOCK (); + LIST_READ_LOCK (); mmap_list *map_list = mmapped_areas.get_list_by_fd (-1, NULL); const size_t pagesize = wincap.allocation_granularity (); @@ -800,7 +802,7 @@ mmap_is_attached_or_noreserve (void *addr, size_t len) } } out: - LIST_UNLOCK (); + LIST_READ_UNLOCK (); return ret; } @@ -1043,7 +1045,7 @@ go_ahead: if (noreserve (flags) && (!anonymous (flags) || !priv (flags))) flags &= ~MAP_NORESERVE; - LIST_LOCK (); + LIST_WRITE_LOCK (); map_list = mmapped_areas.get_list_by_fd (fd, &st); /* Test if an existing anonymous mapping can be recycled. */ @@ -1096,7 +1098,7 @@ go_ahead: ret = base; out_with_unlock: - LIST_UNLOCK (); + LIST_WRITE_UNLOCK (); out: @@ -1144,7 +1146,7 @@ munmap (void *addr, size_t len) } len = roundup2 (len, pagesize); - LIST_LOCK (); + LIST_WRITE_LOCK (); /* Iterate over maps, unmap pages between addr and addr+len in all maps. */ mmap_list *map_list, *next_map_list; @@ -1180,7 +1182,7 @@ munmap (void *addr, size_t len) } } - LIST_UNLOCK (); + LIST_WRITE_UNLOCK (); syscall_printf ("0 = munmap(): %p", addr); return 0; } @@ -1197,19 +1199,20 @@ msync (void *addr, size_t len, int flags) pthread_testcancel (); - LIST_LOCK (); - if (((uintptr_t) addr % wincap.allocation_granularity ()) || (flags & ~(MS_ASYNC | MS_SYNC | MS_INVALIDATE)) || ((flags & (MS_ASYNC | MS_SYNC)) == (MS_ASYNC | MS_SYNC))) { set_errno (EINVAL); - goto out; + syscall_printf ("%R = msync()", ret); + return ret; } #if 0 /* If I only knew why I did that... */ len = roundup2 (len, wincap.allocation_granularity ()); #endif + LIST_READ_LOCK (); + /* Iterate over maps, looking for the mmapped area. Error if not found. */ LIST_FOREACH (map_list, &mmapped_areas.lists, ml_next) { @@ -1239,7 +1242,7 @@ msync (void *addr, size_t len, int flags) set_errno (ENOMEM); out: - LIST_UNLOCK (); + LIST_READ_UNLOCK (); syscall_printf ("%R = msync()", ret); return ret; } @@ -1265,7 +1268,7 @@ mprotect (void *addr, size_t len, int prot) } len = roundup2 (len, pagesize); - LIST_LOCK (); + LIST_WRITE_LOCK (); /* Iterate over maps, protect pages between addr and addr+len in all maps. */ mmap_list *map_list; @@ -1300,7 +1303,7 @@ mprotect (void *addr, size_t len, int prot) } } - LIST_UNLOCK (); + LIST_WRITE_UNLOCK (); if (!in_mapped) {
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